U.S. Marines are on the ground in Yemen to deal with the aftermath of an attack on the U.S. Embassy in the capital city of Sanaa, as the Obama administration warns of sustained protests outside diplomatic posts across the Middle East and North Africa. 

Pentagon spokesman George Little told Fox News the team is in Yemen as a "precautionary measure." 

The move comes as Reuters reports that protesters jumped over U.S. Embassy walls in both Sudan and Tunisia. Reuters reports that protesters also set fire to trees and broke windows inside the U.S. Embassy compound in Tunis. 

A senior U.S. official, without explaining the extent of the breach in the latter attack, told Fox News that Tunisian security forces "have responded effectively" so far to the incident. 

"We're keeping a close eye on events there, but for the moment, the Tunisians are doing precisely what they should do in the face of such events," the official said. 

One official also reportedly claimed that protesters in Sudan have been expelled. Witnesses said Sudanese police opened fire on those trying to climb the walls. 

That is just a snapshot of the violent unrest playing out Friday, in the widest protests yet across the Muslim world. 

One protester was killed in the northern Lebanese city of Tripoli in clashes with security forces, after a crowd of protesters set fire to a KFC and an Arby's restaurant. Protesters hurled stones and glass at police in a furious melee that left 25 people wounded, 18 of them police. 

Security forces in Egypt and Yemen fired tear gas and clashed with protesters to keep them away from U.S. embassies. And Germany's Foreign Minister says the country's embassy in the Sudanese capital of Khartoum has been stormed by protesters and set partially on fire. 

The intense demonstrations, purportedly by people upset over an anti-Islam film, follow warnings by the State Department that the protests could spread across the region. The department, on its Twitter account, cautioned Thursday of sustained protests in Egypt, Oman and Jordan, among other places. 

The Department of Homeland Security and the FBI also issued a joint intelligence bulletin warning that the violent outrage aimed at U.S. embassies could be spread to America by extremist groups.   

In a statement to Fox News, a DHS official said that there is no specific, credible information at this time to indicate that the attacks have increased the threat of violent reaction in the U.S., but it will continue to identify potential threats and take appropriate measures. 

Four Americans were killed in an attack on the U.S. Consulate in Benghazi, Libya, on Tuesday. A Marine unit was dispatched earlier in the week to Tripoli, to help fortify the U.S. Embassy there in the wake of the attack in the eastern part of the country. 

The Associated Press contributed to this report.