Pentagon press secretary George Little said the decision to dispatch about 50 Marines to Sanaa was partly in response to the violence and partly as a precautionary measure.
The Marines are members of a platoon from a Fleet Antiterrorism Security Team, a specially trained and configured group that makes short-notice deployments in response to terrorist threats and to reinforce security at U.S. embassies.
A similar team was dispatched to Tripoli, Libya, on Wednesday in response to the deadly consulate attack in Benghazi that killed U.S. Ambassador Chris Stephens and three other Americans.
Little said no other such teams had been sent to Cairo or other Arab capitals, such as Tunis and Khartoum, where protesters have been demonstrating over the video that mocks the Prophet Mohammed.
A senior U.S. official said that since the attack on the consulate in Benghazi, U.S. intelligence services have deployed extra surveillance equipment over Libya's populated areas. That equipment was added to the surveillance drones that have flown over the region at least since the Libyan revolution last year.
The official would not confirm the type nor which U.S. agency was running them.The deployment to Yemen came as that Arab nation's security forces were firing live rounds and tear gas into the crowd of about 2,000 protesters trying to march to the U.S. embassy.
At the State Department, another senior official said the agency was "working with our personnel and missions overseas and host governments to strengthen security in all locations and to respond effectively where protests have turned violent." Both officials spoke on condition of anonymity because they were not authorized to speak publicly.
U.S. diplomats were in particularly close consultations with the governments of Tunisia and Sudan to ensure that American lives and property are protected, the official said, adding that the Obama administration appreciated statements from leaders in the region who have spoken out against violence and called for calm.
Meanwhile, the official said, the State Department has set up a round-the-clock crisis monitoring team to coordinate information and responses to developments on the ground. The official said the department was also working with diplomatic missions abroad to protect Americans and warn them if violence is imminent or expected.
Associated Press writers Matthew Lee, Robert Burns, Kimberly Dozier and Lolita Baldor contributed to this report.