Demonstrations continued for a fourth day across the Muslim world over an American-made anti-Islamic video. U.S. and other foreign missions have stepped up security following violent attacks that began Tuesday.

Protesters in several cities across the Middle East, south and east Asia and Africa spread out after midday prayers Friday, denouncing the video and those they feel have not done enough to stop it.

Demonstrations continued near the U.S. embassy in Cairo, with protesters throwing rocks at riot police, who responded with tear gas.

The violence also appeared to be spreading to Sudan, where demonstrators are reported to have breached the German embassy. Protests were also reported in Malaysia and Indonesia and security was tight in Kabul, Afghanistan.

In Benghazi, Libya, where the U.S. ambassador and three other American personnel were killed in an attack Tuesday, security was stepped up around the city and the airport temporarily closed.

U.S. warships are headed to the Libyan coast, while additional U.S. marine guards were deployed to protect the American embassy in Yemen, breached by protesters Thursday.

In many Cairo mosques Friday, the video, a crudely-made attempt to mock the Prophet Muhammad, was the topic of the day. One imam reminded worshippers that Egyptians, under their new, Islamist government, can now openly defend the prophet from such insults.

Egyptian President Mohamed Morsi, who has condemned the video, spoke out again Friday on the need to keep protests in check.

Egyptian security forces were building a barrier Friday to block the route to the embassy. Egyptian police used tear gas earlier to break up the protests.

U.S. President Barack Obama spoke Thursday about the relationship between the U.S. and Egypt.

“I don't think that we would consider them an ally, but we don't consider them an enemy. They are a new government that's trying to find its way. They were democratically elected. I think we have to see how they respond to this incident.”

Libyan officials said Thursday that they have arrested four people in connection with this week's assault on the U.S. consulate in Benghazi that killed U.S. Ambassador Christopher Stevens and three of his staff. The officials did not provide details.

American intelligence agencies are examining the alleged involvement of pro-al-Qaida militants. But they say they do not have solid evidence.

U.S. Secretary of State Hillary Clinton condemned the amateur U.S.-made movie that mocks the Islamic Prophet Muhammad. She called it “disgusting” and “reprehensible.”