Around 600 troops from Serbia, Italy, Romania and Turkey are taking part in the "NATO-Serbia" exercise, alongside military planners and observers from several Alliance countries, the ministry said.

It is the first military exercise conducted directly with NATO, which remains a sensitive subject in Serbia following the Alliance's 1999 air campaign against Yugoslavia during the Kosovo war.

Photographs released Tuesday showed Serbian and NATO soldiers now standing side by side at a military training ground near Bujanovac in southern Serbia, alongside armoured vehicles from both forces.

The tactical exercise will run until May 23 under NATO's Partnership for Peace programme, which Belgrade said "respects Serbia's military neutrality".

"The cooperation is aimed at preserving peace and stability in the region," the ministry said.

Serbia is one of the few Balkan countries not in the Alliance, with Belgrade insisting on a long-held policy of neutrality while enjoying close ties with both NATO and Russia.

Serbia has been part of the Partnership for Peace programme for nearly two decades, and regularly participates in drills with NATO members.

The country has also invested heavily in arms over the past decade, buying weapons from NATO member states as well as Russia and China.

"This is an important training activity. It will be hosted by Serbia and conducted in full respect of Serbia's stated policy of military neutrality," a NATO official told AFP ahead of the exercise.

NATO-led peacekeeping force has remained deployed in Kosovo since the end of the war in Serbia's former province, whose independence Belgrade has never recognised.