Rioters set fire to the US embassy in Belgrade on Thursday, killing one person, while more than 90 people were injured in clashes with Serbian police in unrest following Kosovo's independence.
The burnt body found in the embassy was not identified, but an embassy spokeswoman said the person was not a staff member.
"All embassy staff are accounted for," Rian Harris said.
Thirty-two police officers were among those injured in the clashes, which followed a large but peaceful protest against Kosovo's declaration of independence on Sunday.
Down the road from the US embassy, a German embassy guard house was burning, while a car was on fire outside the Canadian diplomatic mission. Other embassies targeted included those of Bosnia, Croatia and Turkey.
With no police in sight, several hundred young men dressed in hooded sports tops and scarves threw flares and stormed the US mission, sparking a fire that blazed for more than an hour.
The US State Department lodged a formal complaint with the Serbian government and called the situation "intolerable".
Other embassies were also targeted in the hours-long rampage, mainly those of Western countries that have recognised Kosovo's independence from Serbia, whose opposition to the move is backed by Russia in the UN Security Council.
The rampage came after more than 150,000 people staged a peaceful protest in front of the old Yugoslav parliament nearby, in a government-organised rally against Kosovo independence.
The US State Department's third highest ranking diplomat, Nicholas Burns, called Serbian Prime Minister Vojislav Kostunica and Foreign Minister Vuk Jeremic to protest the storming.
"The message was very clear: that the situation was intolerable; they needed to act immediately to provide the adequate security forces so that our embassy compound and our personnel were not under attack," State Department spokesman Sean McCormack told reporters.
"We received assurances from the PM Kostunica that there would not be a repeat of this episode and we will hold him to that."
UN Security Council members "condemn in the strongest terms the mob attacks against embassies in Belgrade" said a statement read by Panama's UN Ambassador Ricard Arias, the council chair this month.
EU foreign policy chief Javier Solana, who on Tuesday became the first foreign dignitary to visit Kosovo following its declaration of independence, called the violence "totally unacceptable" and appealed "for calm, restraint and responsibility," said his spokeswoman Cristina Gallach.
But the rioters moved to other parts of the city, setting alight a McDonald's restaurant, ransacking a Levi's clothing shop and using uprooted street signs and even trees to fight police, who detained dozens.
So far, 23 of the 27 EU member states have backed Kosovo's independence, either formally recognising it or declaring their intention to do so. Cyprus, Romania and Spain have explicitly refused to do either. (AFP)