Washington (CNN) -- The U.S. State Department accuses Iran of helping the Syrian government's efforts to suppress protests that have taken place there in recent weeks.
"We believe that there is credible information that Iran is assisting Syria" in quelling the protesters, department spokesman Mark Toner said Thursday.
U.S. officials said the Iranian assistance includes gear used to suppress crowds, as well as equipment and technical advice for monitoring and blocking e-mail, cell phones, text messaging, and internet postings by and among activists.
Syria's Foreign Ministry told the nation's official news agency, SANA, that the claim is "absolutely untrue."
An official at Iran's mission to the United Nations said Iran "categorically rejects" the accusation as "totally baseless and unfounded."
He added, "This and similar allegations are in line with the mainstream anti-Iranian propaganda masterminded and propagated by known circles in the United States to tarnish the image of Iran and Syria."
But Toner said of the Iranians, "They continue to play a meddling role in the region."
American officials said Iran's government is also sharing with Syria the best practices it developed during Tehran's crackdown on the "green movement" protesters in 2009.
One security tactic Iran has developed, according to former Pentagon intelligence analyst Michael Rubin, is arresting protesters days later, rather than in the middle of heated street protests.
"What Iran does is, they take photos" of anti-government protesters, Rubin said. "Then they come, over the next two or three weeks, and they will round up people in the middle of the night, where you won't create a spark, where you won't create a backlash.
"That may be what they're trying to teach Syria right now."
The U.S. allegation was first reported in the Wall Street Journal.