Serbia, March 25 -- 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.

Thousands of people gathered Sunday evening in the southern Serbian city of Nis for the main remembrance event featuring top state officials. President Aleksandar Vucic said in a speech that Serbia will never forget its victims.

"Yes, it was a crime!" Vucic said of the bombing campaign. "No one has been held responsi...