A group of about 150 young people broke away from a 1,000-strong rally in downtown Belgrade late on Tuesday and clashed with riot police deployed in the area to prevent riots similar to those that followed Kosovo's declaration of independence early last year.
Police arrested 24 people after a TV crew and a McDonald's restaurant were attacked.
NATO's 78-day bombing campaign, which started on March 24, 1999, paved the way for the secession of Kosovo, which until then had been a Serbian province with a majority ethnic Albanian population.
Serbian sources estimate the death toll as the result of NATO air raids at about 3,000 civilians and 1,000 military, while the number of wounded has been put at over 10,000. U.S.-based Human Rights Watch has said that some 500 people died during the raids.
"The attack on our country was an illegal act," Serbian Prime Minister Mirko Cvetkovic said on Tuesday as Serbia marked the anniversary of the bombing with series of events. "The NATO bombing neither solved problems nor provided peace, stability and the rule of law in Kosovo-Metohija."
Serbian President Boris Tadic told the UN Security Council on Monday that the air raids had seen the "collective" bombing of Serbs.
Kosovo, with a 90% ethnic-Albanian majority, has been formally recognized as a sovereign state by over 50 countries including the U.S. and most EU members since it proclaimed its unilateral independence from Serbia on February 17, 2008.
Belgrade has said it regards Kosovo's declaration of independence as an illegal act. Russia, Serbia's long-time ally and a veto-wielding member of the UN Security Council, has backed Belgrade and refuses to recognize Kosovo as an independent state.
