Belgrade - The US embassy in Serbia closed two hours early Tuesday and warned citizens to avoid downtown Belgrade because of a planned protest by supporters of war crimes suspect Radovan Karadzic. In February, protesters invaded the embassy and set fire in anger at US support of Kosovo's declaration of independence from Serbia. The embassy's website cited the possibility of renewed violence at the rally for Karadzic, the former Bosnian leader indicted for war crimes by the UN tribunal for former Yugoslavia in The Hague. The embassy would close at 3 pm Tuesday, instead of the usual 5 pm, and US citizens should remember that protests in Serbia can "possibly escalate into violence," the statement said. Serb authorities arrested Karadzic last week in Belgrade, ending 12 years on the run. He is charged with crimes including genocide for his role in Bosnia's 1992-95 ethnic war, among them the 1995 Srebrenica massacre of Bosnian Muslim men and boys.