BERLIN, June 21 — Hundreds of people ran riot in Germany's Stuttgart city centre in the early hours of today, throwing stones and bottles at police and plundering stores after smashing shop windows.

Several arrests were made, a police spokesman told AFP, adding that he did not have a firm figure of the number detained.

Some police officers were also hurt, he said.

Tensions built up shortly after midnight when increasing numbers of people began gathering close to the city's biggest square, the Schlossplatz.

Clashes then broke out between several small groups, with police estimating around 500 people were involved.

Shops along the neighbouring Koenigstrasse, a key shopping thoroughfare, were attacked and looted.

Police called in reinforcements and said they could not immediately give a reason for the outbreak of violence.

Videos posted on Twitter showed people breaking shop windows, with their goods strewn on the streets.

A jewellery store was completely emptied and a mobile phone shop wrecked, according to regional broadcaster SWR.

Smaller scale clashes had broken out downtown last week between police and groups of young people. — AFP