NEW YORK — Anti-American rage that began this week over a video insult to Islam spread to more than 20 countries across the Middle East and beyond Friday, with violent protests that convulsed the birthplaces of the Arab Spring revolutions, breached two more US embassies, and targeted diplomatic properties of Germany and Britain.
At least six protesters were killed and dozens of people were wounded in the demonstrations, from North Africa to Southeast Asia and Indonesia.
The broadening of the protests appeared to reflect a pent-up resentment of Western powers in general, and defied pleas for restraint from world leaders including the new Islamist president of Egypt, Mohammed Morsi, whose country was the instigator of the demonstrations that erupted four days earlier on the anniversary of the Sept. 11, 2001, attacks.
The anger in some cases was surprisingly destructive. In Tunis, a US-run school that was untouched during the revolution nearly two years ago was completely ransacked. In western Afghanistan, protesters burned an effigy of President Obama, who had made an outreach to Muslims a thematic pillar of his first year in office.
The State Department confirmed protesters had penetrated the perimeters of the US embassies in the Tunisian and Sudanese capitals, and said that 65 embassies or consulates had issued emergency messages about threats of violence and that those facilities in Islamic countries were curtailing diplomatic activity.
The Pentagon said a rapid response team of 50 Marines had arrived in Sana, Yemen, to secure the American diplomatic compound, which was damaged by enraged protesters Thursday. Another elite unit of Marines was being sent to Sudan, officials said.
Police said at least three protesters were killed and 28 people were wounded in the attack on the US Embassy in Tunis, the birthplace of the Arab Spring revolutions. It was at least the fourth time that an American diplomatic facility in the Mideast had been breached since the protests began.
In Yemen, baton-wielding security forces backed by water cannons blocked streets near the US Embassy a day after protesters breached the outer security perimeter there, and officials said two people were killed in clashes with the police.
In Lebanon, one person was killed and 25 injured as protesters attacked American fast-food restaurants.
Police in Cairo prevented protesters from getting near the US Embassy, firing tear gas and deploying armored vehicles in a fourth day of clashes in the Egyptian capital.
The wave of unrest not only increased concern in the West but raised new questions about political instability in Egypt, Tunisia, and other Middle East countries where newfound freedoms, once suppressed by autocratic leaders, have given way to an absence of authority.
The protests also seemed to highlight the unintended consequences of US support of movements to overthrow those autocrats, which have empowered Islamist groups that remain implacably hostile to the West.
“We have, throughout the Arab world, a young, unemployed, alienated, and radicalized group of people, mainly men, who have found a vehicle to express themselves,’’ Rob Malley, the Middle East-North African program director for the International Crisis Group, a consulting firm, said in a telephone interview from Tripoli.
In a number of these countries, particularly Egypt and Tunisia, he said, ‘‘the state has lost a lot of its capacity to govern effectively. Paradoxically, that has made it more likely that events like the video will make people take to the streets and act in the way they did.’’
J. Christopher Stevens, the American ambassador in Libya, was killed Tuesday in an attack in Libya. The bodies of Stevens and three other Americans killed in the Libya attack were returned to the United States on Friday. Obama, Secretary of State Hillary Rodham Clinton, and other top officials attended the return ceremony at Andrews Air Force Base.
Some of the most serious violence Friday targeted the compound housing the German and British embassies in Khartoum, the Sudanese capital, causing minor damage to the British property but major fire damage to the German one.
The foreign ministers of both countries protested the assault, which the Associated Press said had been instigated by a prominent sheik exhorting protesters to storm the German Embassy to avenge what he called anti-Muslim graffiti on Berlin mosques.
The police fired tear gas to drive off the attacks in Khartoum, where about 5,000 demonstrators had massed, news reports said, before they moved on to the US Embassy on the outskirts of the capital.
In Tunis, the US Embassy was assaulted at midday by protesters who smashed windows and set fires before security forces routed them in deadly clashes. The worst damage was inflicted on the American Cooperative School of Tunis, a highly regarded institution that catered mostly to the children of non-American expatriates.
School officials, who had sent the 650 pupils home early, said a few protesters scaled the fence and dismantled monitoring cameras, followed by 300 to 400 others, some of them local residents, who looted everything including 700 laptop computers, musical instruments, and the safe in the director’s office, then set the building on fire.
''It’s ransacked,’’ the director, Allan Bredy, said in a telephone interview. ‘‘We were thinking it was something the Tunisia government would keep under control.’’
Thousands of Palestinians joined demonstrations after Friday prayer in the Gaza Strip. Since there is no US diplomatic representation in Gaza, the main gathering took place in Gaza City, outside the Parliament building, where US and Israeli flags were placed on the ground for the crowds to stomp. Some demonstrators chanted, ‘‘Death to America and to Israel!’’ Palestinians also clashed with Israeli security forces in Jerusalem and held protests in the West Bank.
In the eastern Libyan city of Benghazi, militias fired rockets at what they thought were US drones overhead, prompting the government to temporarily close the airport as a precaution.
In Nigeria, troops fired into the air to disperse protesters marching on the city of Jos, Reuters reported. In Syria, about 200 protesters chanted anti-American slogans outside the long-closed US Embassy in Damascus, news reports said.
In the Egyptian Sinai, a group of Bedouins stormed an international peacekeepers’ camp and set fire to an observation tower, according to Al Ahram Online, a state-owned website.
In Iraq, where the heavily fortified US Embassy stands inside the Green Zone and is out of reach to most Iraqis, thousands protested after Friday prayer, in Sunni and Shi’ite cities alike. Iraqis called for the expulsion of US diplomats from the country and demanded that the US government apologize for the incendiary film and take legal action against its creators.