By Meg Wagner, Melissa Macaya, Mike Hayes, Melissa Mahtani, Veronica Rocha and Fernando Alfonso III, CNN
From CNN's Pamela Brown
The US Capitol Police is asking for additional law enforcement for assistance, including federal authorities, per a source familiar.
The source said there are several suspicious devices outside the Capitol Building.
A separate law enforcement source says the DC Metropolitan Police Department has sent more resources to assist the Capitol Police, including CDU platoons or Civil Disturbance Units.
CNN's Pamela Brown reports. Watch:
From CNN's Adrienne Vogt
CNN’s Alex Marquardt reports from the western side of the US Capitol that throngs of protesters are climbing the steps and terrace of the building in a "significant escalation.”
"I can see at least half a dozen protesters scaling, literally, climbing the walls of the Capitol to get up to where their fellow protesters are," he said.
Police have fired several rounds of tear gas, he reported.
Marquardt said he did not see "any sort of sign of law enforcement" from where he stood.
The US Capitol is currently on lockdown, according to Capitol police officers.
From Ted Barrett, Manu Raju and CNN's Capitol Hill team
The US Capitol has been breached during a tense situation with demonstrators, according to Capitol police officers.
The House doors have been locked and an emergency alert from the Capitol police just transmitted the same thing:
"Due to an INTERNAL threat in the building, take shelter in the nearest office and stay quiet."
Capitol Hill police are also blocking anyone from moving from Senate office buildings into the US Capitol building. There are underground tunnels that link the office buildings with the Capitol building that senators, staff, and journalists use to travel back and forth.
Watch more:
Donald Trump Jr. condemned protesters outside the Capitol building, saying "this is wrong and not who we are."
In a tweet, he urged demonstrators to be peaceful "and use your 1st Amendment rights, but don’t start acting like the other side. We have a country to save and this doesn’t help anyone."
Hundreds of pro-Trump protesters have gathered on the House side of the US Capitol.
Moments ago, Capitol police officers said the building has been breached.
"Due to an INTERNAL threat in the building, take shelter in the nearest office and stay quiet," police said in an alert.
Congress is now in recess and the electoral certification process has been paused.
Here's a look at the scene on Capitol Hill right now:
Top House Republican Kevin McCarthy is urging demonstrators outside of the US Capitol to "remain peaceful."
The US Capitol is currently on lockdown, according to Capitol police officers. Congress is in session right now to count and certify the Electoral College votes for president and vice president.
See his tweet:
Watch:
From CNN’s Peter Nickeas
Shortly after 1 p.m. ET pro-Trump protesters pushed through barriers set up along the perimeter of the US Capitol Building. They tussled with officers in full riot gear, some calling officers "traitors" for doing their jobs.
Protesters could be seen pushing against metal fences, and police using the fences to push protesters back, while other officers reached over the top to club people trying to cross their lines.
Flash bangs could be heard near the steps of the Capitol as smoke filled the air. In some instances officers could be seen deploying pepper spray.
Teargas has been deployed, but it’s not clear whether by protesters or police, and people wiped tears from their eyes while coughing.
Trump supporters chanted "USA" and waved American flags as well as flags reading "Don’t Tread on Me."
From CNN's Aditi Sangal
Pennsylvania GOP Sen. Pat Toomey criticized his GOP colleagues' objections to Arizona's electoral results.
"Why are the objectors objecting only to swing states that President Trump lost? What about the ones he won? I don't know, North Carolina? What about California?," the senator said.
He added:
"If Congress gets to decide which states get to vote in the electoral college, then clearly Congress is selecting the President, not the people. Whichever party controls both houses of congress would control the presidency. The public would never tolerate Congress picking the president."
Toomey emphasized that Congress has no authority under the US Constitution to overturn the results of an election.
"I voted for President Trump. I publicly endorsed President Trump. I campaigned for President Trump. I did not want Joe Biden to win this election. But there's something more important to me than having my preferred candidate sworn in as the next president and that's to have the American people's chosen candidate sworn in as the next president," he concluded.
From CNN's Adrienne Vogt
As US Capitol police said the Capitol is on lockdown amid a tense situation with demonstrators outside, Democratic Rep. Elaine Luria tweeted that she had to evacuate her office.
"I don’t recognize our country today and the members of Congress who have supported this anarchy do not deserve to represent their fellow Americans," Luria added in another tweet.