BELGRADE , Serbia ( CNN ) -- The U.S. Embassy in Belgrade is evacuating all nonessential personnel following Thursday 's attack on the building by a crowd of protesters , a spokesman for the embassy told CNN Friday . Serbian riot police stand in front of the damaged U.S. Embassy in Belgrade on Friday . The U.S. ambassador , Cameron Munter , is staying , officials said . The embassy was closed Friday , and a handful of riot police holding shields stood outside the building , its outer walls blackened from fires set the night before and some of its windows smashed . It will remain closed until Monday or Tuesday so officials can assess the damage , said Bill Wanlund , the embassy 's spokesman . He said embassy staff were still in a heightened state of alert but there were no specific threats against any staff members . The United States has warned the Serbian government that it has a responsibility to protect its assets . A top U.S. diplomat was asked during an interview on CNN if the Serbian government `` gets '' the warning . `` They 'd better get it , because they have a fundamental responsibility to protect our diplomats and our embassy and to protect American citizens , '' said Undersecretary of State for Political Affairs R. Nicholas Burns . `` What happened yesterday in Belgrade was absolutely reprehensible . '' Watch Burns ' angry comments on Belgrade attack » . Thursday 's violence erupted after demonstrations by thousands of Serbs against Kosovo 's declaration of independence . The anger directed against the United States and other countries for recognizing the breakaway province as a nation sparked attacks on Western embassies and shops by hundreds of people . Burns said there was an `` insufficient '' number of security people guarding the U.S. Embassy at a demonstration everyone knew would take place . He said security `` melted away '' as `` the mob attacked our embassy . '' `` This kind of thing should not happen in a civilized country . It does n't happen in the United States of America . It does n't happen in most world capitals . So the Serb government needs to reflect seriously about the responsibility it has under the Vienna Convention , '' he said . Burns , the third highest ranking diplomat in the State Department , said he told the Serbian prime minister , Vojislav Kostunica , and his government that the U.S. `` would hold them personally responsible for the safety of our people . '' `` They assured me that they would have adequate security on the ground today and for every day to come . We will hold them to that commitment , '' Burns said . Demonstrators only managed to break into one U.S. embassy building , which Wanlund said was rarely used by staff . He said the protesters did n't manage to get any documents or embassy materials . Only Marines and security guards were present at the embassy when the angry mob of about 100 approached the walls . In addition to the U.S. Embassy , the protesters attacked other Western interests including the embassies of Britain and Germany , as well as a McDonald 's restaurant and a Nike shop . `` One might understand the emotion , but not the violence , and that 's what the Serb government needs to remember , '' Burns said . Burns , who is stepping down in March , has long been involved in trying to resolve tensions in the former Yugoslavia . The situation was complicated by Sunday 's unilateral declaration of independence by Serbia 's predominantly Albanian region of Kosovo . Kosovo is revered historically by Orthodox Christian Serbs but also is claimed as separate and distinct by its ethnic Muslim Albanians . The wisdom of recognizing Kosovo independence has been questioned by many observers , who say the United States wo n't recognize other unilateral declarations of independence . Some opponents of Kosovo 's independence say recognition is a bad precedent if it 's unilateral and not done in a bilateral , diplomatic setting . They say it will give others the incentive to stage their own breakaway nations . Burns said every situation has its unique set of circumstances , as does Kosovo , which was the victim of ethnic cleansing policies by the Slobodan Milosevic regime in 1999 . NATO troops fought Serbia in an air war then and pushed Serbian forces out of the region . Since then Kosovo has been run by the United Nations and with security supplied by NATO forces . E-mail to a friend .
U.S. : An event like embassy attack `` should not happen in a civilized country '' U.S. warns Serbia of responsibility to protect U.S. diplomats , building . Embassy evacuating nonessential personnel ; ambassador will stay in Belgrade . The United States has warned that it is prepared to evacuate its diplomatic staff from the Serbian capital if there are further attacks on American diplomats.