A demonstrator stands in front of a burning street barricade during clashes at the so-called street party "Schanzenfest" in the Schanze district in Hamburg August 20, 2011. [Photo/Agencies]

HAMBURG - Police used water cannons to disperse rioters in the German city of Hamburg Saturday night and early Sunday, after an annual street festival turned violent.

Two policemen suffered minor injuries, while some 30 people were taken into custody during the confrontation between the police and the rioters, a police spokeswoman said.

"It was only when the festival as such ended that there were several arson attacks and attacks against property that made police intervention necessary," spokeswoman Karina Sadowsky said.

The violence broke out as the youths attending the Schanzenfest, an annual street festival which drew some 10,000 people at presence and proceeded into night in the Schanzenviertel district of Hamburg, spiraled out of control.

Masked youths threw fireworks in the evening and set fire to piles of rubbish on the roads. Passers-by put the fires out.

The police source said rioters then tried to break into a branch of the Sparkasse bank with a wooden beam to smash through the front door, before setting fire in front of the bank.

They also pelted bottles, rocks and fireworks at the police, as the commotions went on more hectically on late Saturday and in the wee hours of Sunday.

Four police cars were damaged and a BMW sedan was set ablaze.

The Schanzenfest, an annual event since 1988, saw 14 people injured and 42 arrested last year.

Police forces remove a street barricade during clashes at the so-called street party "Schanzenfest" in the Schanze district in Hamburg August 20, 2011. [Photo/Agencies]