Police officers and demonstrators during a rally on the 65th anniversary of the Allied bombing of Dresden, Germany. ((Matthias Rietschel/Associated Press) )

Thousands of neo-Nazis and their opponents protested Saturday in the eastern German city of Dresden on the 65th anniversary of the deadly Allied bombing at the end of the Second World War.

Heavy security was in place to prevent clashes between the two groups, with five police helicopters overhead monitoring the crowds. Though some stones and snowballs were thrown, police said so far the two sides have largely been kept separate.

Far-right organizers have characterized the event as a "mourning march," while mainstream political parties and civic groups were equally determined to protest far-right attempts to exploit the city's painful history.

Three successive waves of British and U.S. bombers set off firestorms and destroyed Dresden's centuries-old baroque city centre on Feb. 13-14, 1945.

The total number of people estimated killed in the bombing ranges from a low 2008 estimate of 25,000 people to previous scholars' estimates that ran as high as 135,000.

Leaders of Germany's far-right fringe have, in the past, sparked outrage by comparing the bombing of Dresden to the Holocaust.

Mayor Helma Orosz said Saturday that she hoped thousands would join a human chain symbolically protecting the restored city centre from neo-Nazis, after the city mounted an unsuccessful legal challenge to block the far-right march.

Police braced for up to 7,000 far-right supporters from Germany and other European countries but so far only 1,300 had arrived, police spokesman Thomas Geithner said Saturday morning.

"The most important task for us is to keep both blocks separated and not to allow them any contact," Geithner said.

About 2,000 left-wing counter-demonstrators gathered a few hundred metres away, with many trying to block roads to prevent far-right supporters from reaching their assembly point.

Karolin Hanebuth, 20, came from Hannover in western Germany to counter the far-right protest.   

"Fascism is not an opinion, it is a crime," she told The Associated Press.

The far right is marginal in Germany and has no seats in the national parliament. However, Saxony, where Dresden is located, is one of two eastern German states where the far-right National Democratic Party has seats in the regional legislature.

After the bombing, Dresden was painstakingly rebuilt over many decades. Its landmark domed Frauenkirche, or Church of Our Lady — for decades no more than a mound of rubble — reopened in 2005.