Thousands of protesters have gathered in the eastern German city of Dresden for competing demonstrations marking 65 years since Allied forces bombed the city toward the end of the second world war.

Clashes broke out on Saturday in the centre of the city where about 5,000 neo-Nazi protesters faced off with an estimated 10,000 leftist demonstrators.

The leftist supporters had gathered across the Elbe river, joining hands to create a human chain to try and prevent the neo-Nazis from staging a march.

More than 4,000 German police officers were deployed to prevent clashes between the two groups, but Natalie Steger, a correspondent for Germany's ZDF Channel, told Al Jazeera that security officials had difficulty keeping the order.

"The police really have a hard time because they're trying to separate these two groups - the neo-Nazis, which want to march and the left-wing people."

Scuffles also broke out between police and protesters from both sides, with several barricades set on fire and some minor injuries reported.

'Bombing Holocaust'

The February 13 anniversary of the bombing of Dresden has become a focus for neo-Nazi groups in the past few years. Some far-right politicians have also sparked controversy by describing the raids as a "bombing Holocaust".

But Helma Orosz, the mayor of Dresden, said the city does not want the neo-Nazis there, the Associated Press news agency reported.

The human chain helped "make Dresden a fortress against intolerance and stupidity, and the anniversary provided a reminder of who started the war", Orosz said.

The Dresden air raids are considered one of the most controversial attacks by Allied forces during World War II.

More than 30sq km of the historic city was destroyed in heavy bombing by US and British forces.

The number of civilian casualties is disputed, with estimates ranging from 25,000 to more than 100,000 people killed in the raids.