PHOTO: CNN
Now playing
00:55
Carrie Lam says Hong Kong protesters are hurting economy
Passengers look out at American Airlines flight 718, a Boeing 737 Max, parked at its gate at Miami International Airport as people load for the flight to New York on December 29, 2020 in Miami, Florida. The Boeing 737 Max flew its first commercial flight since the aircraft was allowed to return to service nearly two years after being grounded worldwide following a pair of separate crashes. (Photo by Joe Raedle/Getty Images)
Passengers look out at American Airlines flight 718, a Boeing 737 Max, parked at its gate at Miami International Airport as people load for the flight to New York on December 29, 2020 in Miami, Florida. The Boeing 737 Max flew its first commercial flight since the aircraft was allowed to return to service nearly two years after being grounded worldwide following a pair of separate crashes. (Photo by Joe Raedle/Getty Images)
PHOTO: Joe Raedle/Getty Images
Now playing
03:15
Airlines & TSA boost security ahead of Inauguration
Philanthropist Chief Executive Officer of Las Vegas Sands Sheldon Adelson listens to US President Donald Trump address to the Israeli American Council National Summit 2019 at the Diplomat Beach Resort in Hollywood, Florida on December 7, 2019. (Photo by MANDEL NGAN / AFP) (Photo by MANDEL NGAN/AFP via Getty Images)
Philanthropist Chief Executive Officer of Las Vegas Sands Sheldon Adelson listens to US President Donald Trump address to the Israeli American Council National Summit 2019 at the Diplomat Beach Resort in Hollywood, Florida on December 7, 2019. (Photo by MANDEL NGAN / AFP) (Photo by MANDEL NGAN/AFP via Getty Images)
PHOTO: Mandel Ngan/AFP/Getty Images
Now playing
03:14
Major GOP donor and casino magnate Sheldon Adelson dies
Democratic presidential candidate and former US Vice President Joe Biden speaks on the state of the US economy on September 4, 2020, in Wilmington, Delaware. (Photo by JIM WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images)
Democratic presidential candidate and former US Vice President Joe Biden speaks on the state of the US economy on September 4, 2020, in Wilmington, Delaware. (Photo by JIM WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images)
PHOTO: JIM WATSON/AFP/Getty Images
Now playing
02:02
Why Wall Street is hopeful about Biden despite economic challenges
Now playing
05:39
Ben & Jerry's calls for Trump's removal
This illustration picture shows the social media website from Parler displayed on a computer screen in Arlington, Virginia on July 2, 2020. - Amid rising turmoil in social media, recently formed social network Parler is gaining with prominent political conservatives who claim their voices are being silenced by Silicon Valley giants. Parler, founded in Nevada in 2018, bills itself as an alternative to "ideological suppression" at other social networks. (Photo by Olivier Douliery/AFP/Getty Images)
This illustration picture shows the social media website from Parler displayed on a computer screen in Arlington, Virginia on July 2, 2020. - Amid rising turmoil in social media, recently formed social network Parler is gaining with prominent political conservatives who claim their voices are being silenced by Silicon Valley giants. Parler, founded in Nevada in 2018, bills itself as an alternative to "ideological suppression" at other social networks. (Photo by Olivier Douliery/AFP/Getty Images)
PHOTO: Olivier Douliery/AFP/Getty Images
Now playing
03:49
Parler sues Amazon in response to being deplatformed
Panasonic
Panasonic's Augmented Reality Heads-up Display
PHOTO: Panasonic USA
Now playing
01:06
This tech gives drivers directions on the road in front of them
PHOTO: Wimkin
Now playing
03:18
The online warning signs of the violent Capitol siege
PHOTO: Twitter
Now playing
02:39
Twitter permanently suspends Donald Trump from platform
PHOTO: CNN
Now playing
03:56
'What are we supposed to do?': Rioter speaks to CNN reporter
President Donald Trump arrives to speak at a rally protesting the electoral college certification of Joe Biden as President, Wednesday, Jan. 6, 2021, in Washington. (AP Photo/Evan Vucci)
President Donald Trump arrives to speak at a rally protesting the electoral college certification of Joe Biden as President, Wednesday, Jan. 6, 2021, in Washington. (AP Photo/Evan Vucci)
PHOTO: Evan Vucci/AP
Now playing
01:38
Facebook blocks Trump through end of presidency
PHOTO: CNN
Now playing
02:56
CNN speaks to Trump supporters about Trump's election lies
NEW YORK, NY - JUNE 3: The Google logo adorns the outside of their NYC office Google Building 8510 at 85 10th Ave on June 3, 2019 in New York City. Shares of Google parent company Alphabet were down over six percent on Monday, following news reports that the U.S. Department of Justice is preparing to launch an anti-trust investigation aimed at Google. (Photo by Drew Angerer/Getty Images)
NEW YORK, NY - JUNE 3: The Google logo adorns the outside of their NYC office Google Building 8510 at 85 10th Ave on June 3, 2019 in New York City. Shares of Google parent company Alphabet were down over six percent on Monday, following news reports that the U.S. Department of Justice is preparing to launch an anti-trust investigation aimed at Google. (Photo by Drew Angerer/Getty Images)
PHOTO: Drew Angerer/Getty Images North America/Getty Images
Now playing
03:25
Google employee on unionizing: Google can't fire us all
FILE - In this undated file photo issued by the University of Oxford, a researcher in a laboratory at the Jenner Institute in Oxford, England, works on the coronavirus vaccine developed by AstraZeneca and Oxford University. Britain on Wednesday, Dec. 30, authorized use of a second COVID-19 vaccine, becoming the first country to greenlight an easy-to-handle shot that its developers hope will become the "vaccine for the world." The Department of Health said it had accepted a recommendation from the Medicines and Healthcare Products Regulatory Agency to authorize the vaccine developed by Oxford University and U.K.-based drugmaker AstraZeneca.  (John Cairns/University of Oxford via AP, File)
FILE - In this undated file photo issued by the University of Oxford, a researcher in a laboratory at the Jenner Institute in Oxford, England, works on the coronavirus vaccine developed by AstraZeneca and Oxford University. Britain on Wednesday, Dec. 30, authorized use of a second COVID-19 vaccine, becoming the first country to greenlight an easy-to-handle shot that its developers hope will become the "vaccine for the world." The Department of Health said it had accepted a recommendation from the Medicines and Healthcare Products Regulatory Agency to authorize the vaccine developed by Oxford University and U.K.-based drugmaker AstraZeneca. (John Cairns/University of Oxford via AP, File)
PHOTO: John Cairns/University of Oxford/AP
Now playing
02:36
AstraZeneca vaccine provides 'logistical convenience'
President Donald Trump
President Donald Trump's name appears on a stimulus check on May 3, 2020.
PHOTO: Will Lanzoni/CNN
Now playing
03:05
Here's what the new stimulus package means for Americans
PHOTO: Branislav Nenin/Shutterstock
Now playing
02:27
Is working from home the new normal?
(CNN Business) —  

Twitter will no longer accept advertisements from state-controlled media outlets, the company announced Monday, hours after it joined with Facebook to take down a covert Chinese social media campaign that sought to undermine pro-democracy protests in Hong Kong.

“We want to protect healthy discourse and open conversation,” Twitter said in a statement posted on its website.

Twitter said the new policy would only apply to “news media entities that are either financially or editorially controlled by the state.” While state media cannot pay for advertisements that would amplify their message, they will be allowed to continue posting on the platform. Twitter said the new restrictions do not apply to outlets funded by taxpayers, or independent public broadcasters.

The new policy was announced shortly after Twitter said it had identified a network of more than 900 accounts originating in China that “were deliberately and specifically attempting to sow political discord in Hong Kong, including undermining the legitimacy and political positions of the protest movement.” Some accounts called protesters “cockroaches” or compared them to Islamic State terrorists. The offending accounts have been taken down from Twitter and Facebook.

It also came after BuzzFeed News and others reported that media outlets in China, most of which are funded by the state and tightly controlled by authorities in Beijing, had been buying advertisements on Facebook and Twitter that portrayed the protests negatively.

“Although the people behind this activity attempted to conceal their identities, our investigation found links to individuals associated with the Chinese government,” Nathaniel Gleicher, Facebook’s head of cybersecurity policy, wrote in a blog post.

Beijing responded on Tuesday. Geng Shuang, a spokesman for China’s Ministry of Foreign Affairs, told reporters that “people will have their own judgments about what is happening in Hong Kong, and what the truth is.”

“I think it is reasonable that Chinese media use overseas social media to communicate with local people, to tell stories about China, to introduce Chinese policies,” he said.

This is the first time tech companies have pointed the finger at Beijing for covert efforts to influence messaging around the Hong Kong protests. Pro-democracy demonstrators have massed throughout Hong Kong for 11 consecutive weekends.

An account that was titled “Dream News” tweeted about the demonstrators, “We don’t want you radical people in Hong Kong. Just get out of here!”

The accounts posted in multiple languages and at least some of them appeared to target American audiences. One account, that was set up more than 10 years ago, said in its Twitter bio, “Conservative News from the USA and Abroad. #Catholic Defender of the Constitution of the United States.” The account claimed to support President Donald Trump.

Other accounts also purported to be operated by people in the United States, listing locations like Chicago and Long Beach, California.

Twitter initially identified the network and shared details about the accounts with Facebook (FB). Then, Facebook (FB) identified about a dozen pages, accounts and groups that were tied to the operation.

The Facebook pages were followed by about 15,000 accounts, the company said.

Twitter (TWTR) said many of the accounts accessed its platform using virtual private networks because Twitter (TWTR) is blocked in China.

China, of course, is not alone in using social media to spread unrest. Covert campaigns have been tied to Russia and Iran, among other countries.

In 2018 the US Department of Justice brought charges against a Kremlin-linked troll group that posed as American on social media in the run-up to the 2016 US presidential election.

-— Joshua Berlinger, Steven Jiang and Nanlin Fang contributed to this report.