Strasbourg -- Police fired tear gas and water cannons in clashes with demonstrators Friday as NATO leaders gathered for a summit in this eastern French city and over the border in Germany.

Officials said two officers were lightly injured, apparently by a firework, during several hours of sparring between riot police and hardcore protesters near an anti-NATO camp on the outskirts of Strasbourg.

The protesters tried but failed to get to the heavily protected venues of the summit talks, protected in huge city centre security zones behind metal barriers and thousands of riot officers.

A coalition of groups has organised a march that is expected to draw tens of thousands of people on Saturday to protest against the summit, western policy and NATO's military operations.

The gathering of NATO's 28 member states, attended by leaders including US President Barack Obama, marks its 60th anniversary and is also focused on beefing up the alliance's operations in strife-torn Afghanistan.

Groups such as the German-based Anti-Nato Koordination say they are against the "imperialism and military barbarism that NATO represents."

With around 25,000 police on standby ahead of Saturday's march, protesters have repeatedly failed to make it to the locked-down centre of Strasbourg.

Protesters said Friday's trouble kicked off after around a hundred people dressed as clowns were turned back to the camp.

A similar number of Black Block militants -- masked, black-clad protesters who are known for clashing with security forces at summits around the world -- then barricaded the camp with waste-bins and wood posts, which they set on fire.

Around a hundred police officers responded by charging the protesters and used water cannons and tear gas to bring them under control.

However, police in most other areas avoided confrontation with the anti-NATO protesters, and did not make any arrests -- in contrast with Thursday, when 300 people were detained and a German photographer was injured.

French far-left leader Olivier Besancenot blasted the "state of siege" in Strasbourg, saying it had made trouble unavoidable.

Over the border in the German spa town of Baden-Baden -- where the leaders of the alliance's member nations including US President Barack Obama were gathering for a gala dinner -- some 800 people marched peacefully.

They carried a banner in German reading "NATO geht Baden Baden," a play on the host city's name meaning "NATO's sinking".

"Sixty years is enough! No to NATO!" chanted the marchers, many of them draped in rainbow peace flags.

Three thousand riot police were deployed in Baden-Baden, and barred the marchers from the centre, where Obama was greeted by Chancellor Angela Merkel before attending a gala concert with his colleagues.

AFP/Expatica