Hundreds run riot, loot shops in Germany.

German authorities expressed shock Sunday over a rampage of an 'unprecedented scale' overnight in the city centre of Stuttgart, where hundreds of party-goers ran riot, attacking police and plundering stores after smashing shop windows.

Two dozen people, half of them German nationals, were arrested provisionally, as police reported 19 colleagues hurt.

'They were unbelievable scenes that have left me speechless. In my 46 years of police service, I have never experienced this,' said Stuttgart police chief Frank Lutz.

Tensions built up shortly after midnight when officers carried out checks on a 17-year-old German man suspected of using drugs, said Stuttgart deputy police chief Thomas Berger.

Crowds who were milling around at the...