Serbia on Monday held commemorations at the sites where scores were killed 15 years ago in NATO air strikes launched to stop a crackdown by Serb forces on independence-seeking Kosovo.

"A nation that forgets its victims and its history is condemned to relive that history," said Prime Minister Ivica Dacic, who laid a wreath at an army headquarters near Belgrade which was frequently targeted by NATO bombs.

In the Serbian capital, a park was opened in memory of 16 people killed in the bombing raid of state broadcaster RTS, and throughout the country schoolchildren were reminded of a painful chapter in the country's history.

The 11-week operation in 1999 was the Atlantic alliance's first-ever major bombing campaign in Europe and remains etched deep in Serbia's public memory despite efforts by the government to move on.

"Today's Serbia conducts peaceful politics to resolve its problems," Dacic said at the commemoration as Serbia is seeking to heal the wartime wounds with Kosovo, its renegade mainly ethnic Albanian province.

On March 24, 1999, NATO began the air strikes -- without UN Security Council backing -- after Serbian strongman Slobodan Milosevic spurned a call to end the crackdown on ethnic Albanian guerrillas fighting for the independence of the southern province.

For 78 days NATO aircraft bombed Serbian military and civilian targets throughout the country, including the capital Belgrade and Kosovo itself, severely damaging infrastructure and leaving hundreds dead.

The civilian death toll has never been officially established and figures vary from 2,500 dead claimed by Serbian officials to 500 in a Human Rights Watch estimate.

The bombings ended on June 10 when Serbia agreed to withdraw its troops from the breakaway region. Kosovo was placed under UN administration, with NATO-led peacekeepers brought in to provide security.

In 2008, Kosovo unilaterally declared independence from Serbia and has so far been recognised by more than 100 countries, including the United States and most of the European Union's 28 member states.

Serbia, backed by Russia, fiercely refuses to recognise the secession, but has nevertheless moved to improve ties with Kosovo for the sake of integration with the European Union.

Having signed an EU-brokered agreement with Pristina on normalisation of relations, Serbia was granted the opening of EU accession talks in January.

In Kosovo, where mainly Serbian positions had also been bombed, only the Serb minority planned to commemorate the NATO campaign which became key for the ethnic Albanians' independence.

Kosovo Prime Minister Hashim Thaci issued a statement calling the NATO campaign "the beginning of the big victory for the republic of Kosovo, a historic day for our people".