BELGRADE, Serbia — Angry Serbs protesting Kosovo's independence stormed the U.S. embassy here last night and set it on fire, as the fringe of a large and generally peaceful demonstration sponsored by the Serbian government turned violent.

Serbian police drove off the protesters, some of whom were chanting "Down with USA terror" and "Kill the Albanians," and firefighters controlled the blaze.

A charred body, which U.S. officials said was unidentified, was found inside the embassy.

At least 96 people were injured, B-92 radio reported, including 32 police officers and four reporters.

The Bush administration filed a formal complaint and accused the Serbian government of failing to protect the embassy. The Serbian government also condemned the violence.

The rampage was the latest in daily demonstrations against Kosovo's announcement Sunday that it is seceding from Serbia. The United States has been among the countries — most of them Western nations — recognizing the new state, while Russia, China and others adamantly oppose the move by the province in the south of Serbia.

"Where is Kosovo? Whose is Kosovo?" Serbian Prime Minister Vojislav Kostunica demanded, his voice cracking with rage as he launched yesterday's demonstration.

"Kosovo belongs to the Serbian people," he said. "There is no force, no threat and no punishment big and hideous enough for any Serb, at any time, to say anything but Kosovo is Serbia!"

An estimated 150,000 Serbs marched from parliament to St. Sava Cathedral in downtown Belgrade and prayed with leaders of the Christian Orthodox Church to lament the loss of Kosovo, a cherished site of the country's religious heritage but also home to some 2 million ethnic Albanians who chafed under Serbian rule.

Analysts maintain that many Serbs are resigned to losing Kosovo and, in fact, the turnout last night fell below the government's expectations.

Still, the "people's rally" was the largest demonstration since Serbs mobilized in October 2000 to oust dictator Slobodan Milosevic.

POLICE STOP ATTACKERS

Observers worried about the violence spreading from Belgrade to Kosovo, where already incidents have flared on the border. Serb protesters yesterday burned tires and threw stones at NATO and U.N. forces guarding the border and blocking the Serbs from crossing.

In Belgrade, Kostunica and other nationalist politicians led the rally. Children got the day off from school and people were bused in.

Much of the rally was peaceful. But groups of young Serbs, some masked and many carrying bottles of beer and plum brandy, began attacking Western embassies, McDonald's restaurants, banks and buses. They torched cars, uprooted traffic lights and rampaged through the streets until reaching the U.S. Embassy.

Some demonstrators squeezed between the metal bars of the embassy gate and soon flames shot from inside the building. One protester climbed on the building, ripped the American flag off its pole and briefly put up a Serbian flag in its place, Reuters reported.

A squad of Serbian police armed with batons was overwhelmed. Reinforcements arrived in armored vehicles, firing tear gas and scattering the crowd, which went on a looting spree, especially at sporting goods stores.

The embassy had been open earlier but was closed at the time of the evening attack. U.S. Marine guards and other security personnel were at the embassy compound when it was attacked, the U.S. State Department said.

U.S. COMPLAINS

U.S. Assistant Secretary of State Nicholas Burns complained in phone calls to Kostunica and Foreign Minister Vuk Jeremic.

"The message was very clear: that the situation was intolerable, that they needed to act immediately," said State Department spokesman Sean McCormack.

Burns "made it very clear to the foreign minister that we would hold the Serbian government personally responsible for the safety and well-being of our embassy employees."

Burns insisted to Serbian leaders that statements inciting violence must cease.

The embassy building will be closed today through Monday as officials take stock of the damage, McCormack said.

U.S.-Serbian relations were already strained. Serbia withdrew its ambassador to Washington this week after American recognition of Kosovo's independence. But Serbian officials said they regret that violence broke out.

Serbia's pro-Western president, Boris Tadic, who was out of the country during the rally, issued a televised appeal to the public to withdraw from the streets and not attack embassies.

"This only keeps Kosovo distant from Serbia," Tadic said.

The U.N. Security Council also condemned the attacks, saying host governments must protect diplomatic premises. The council unanimously condemned "in the strongest terms the mob attacks against embassies in Belgrade" and said that it welcomed "the steps taken by the Serbian authorities to restore order."