Serbia is marking the 10th anniversary of NATO's bombing campaign against it over Kosovo with commemorations honoring the victims and a nationalist gathering denouncing the West.
Schools opened classes Tuesday with a minute of silence for the 2,500 civilians the government says were killed in the 78-day bombing. Air-raid sirens sounded at noon, and officials plan to lay wreaths at bombing sites throughout Serbia.
Serbia's Cabinet also is holding a special session dedicated to the anniversary. Hard-line nationalists have organized an anti-NATO rally in Belgrade later Tuesday.
NATO launched air attacks on Serbia on March 24, 1999, to force then-President Slobodan Milosevic to end a violent crackdown on separatists in Kosovo.
About 15,000 NATO-led peacekeepers remain in Kosovo, which now has diplomatic recognition from 56 nations after declaring unilateral independence from Serbia last year.
On Monday, top officials from Serbia and Kosovo lobbed bitter accusations at each other during a United Nations Security Council meeting on Kosovo.
Kosovo's Foreign Minister Skender Hyseni accused Serbia of blocking his government's participation in regional and international organizations, while Serbian President Boris Tadic accused Kosovo of failing to protect human rights and the Serb minority.
U.N. special envoy Lamberto Zannier says tensions persist in several areas, but the situation in Kosovo is stable.
Some information for this report was provided by AFP and AP.