BELGRADE, Serbia (AP) — Twenty years after NATO intervened to stop Serbia's onslaught in Kosovo, Belgrade on Sunday commemorated the victims of what it says was an aggression while Kosovo hailed the beginning of its national liberation.

The staunchly opposed views of the two former war foes reflect persisting tensions over Kosovo, a former Serbian province whose 2008 declaration of independence Serbia still does not recognize.

Serbian far-right supporters burned NATO and European Union flags in Belgrade, condemning the 78-day bombing that ended the country's rule over the territory many here view as their nation's historic heartland.

Top Serbian officials are to attend a main remembrance ceremony in a southern city later Sunday, while other wreath-lying commemorations were being held throughout the day.

"Serbia is not ashamed to remember those who fought for it and we must never forget that," Interior Minister Nebojsa Stefanovic said at a commemoration in Belgrade.

Rights groups say several hundred people died in the NATO bombing, while Serbia says the number of victims was much higher. The bombing also destroyed much of Serbia's infrastructure.

In Kosovo, leaders said NATO's air war brought freedom for their people as they paid their respects to the victims of the 1998-99 war that killed more than 10,000 people.

"It is wonderful that Kosovo's people are free and children can grow up at their home and can go to their schools and that's only thanks to NATO air campaign," Prime Minister Ramush Haradinaj told The Associated Press.

Serbia and Kosovo have been told they must normalize relations in order to advance in their bids to become members of the EU, but the EU-mediated talks have stalled amid tensions.

Several Western embassies in Belgrade on Sunday issued a joint statement of condolence for the victims of the bombing, pledging to "work even harder to contribute to lasting peace and stability to the region."

"We remember March 24 as the day diplomacy failed, and we express our sincere regret for the loss of civilian lives during the events of 1999," said the statement. "We are saddened for all of those who lost their loved ones during the wars of the 1990s."