Serbia marks Monday the 15th anniversary since NATO launched an air war to stop the crackdown on independence-seeking Kosovo by the regime of strongman Slobodan Milosevic.

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

On March 24 1999, NATO launched the attack -- without UN Security Council backing -- after Milosevic spurned a call to end repression by Serbian forces on ethnic Albanian guerrillas fighting for the independence of Kosovo.

For 78-days NATO aircraft bombed Serbian military and civilian targets throughout the country, including Kosovo and capital Belgrade, severely damaging infrastructure and killing at least hundreds.

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

The bombing ended on June 10 when Serbia agreed to withdraw its troops from the breakaway province. 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 recognized 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 recognize 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 normalization of relations, Serbia was awarded the opening of EU accession talks in January this year.

But even with eyes fixed on a Brussels-bound future, views of the 1999 bombings will always be strong in Belgrade.

In Serbia, the anniversary was to be commemorated by a series of events, including the opening of a Belgrade park in memory of 16 people killed in the controversial bombing of state broadcaster, RTS.

Schools were to devote class time to the anniversary, while top officials were to lay wreaths on a number of sites hit by NATO bombs.

In Kosovo, also severely hit by bombings mostly on Serbian positions, only the Serb minority planned to commemorate with majority ethnic Albanians seeing the campaign as key to their independence. (AFP)