Police arrested 50 people after groups of youths torched cars and lobbed rocks at officers and firefighters in a sixth night of violence in Danish cities, officials said on Saturday.

Youths were arrested overnight in Copenhagen, Aarhus, Ringsted and other towns, a police spokesman said.

Muslims protest in Copenhagen on Friday against the re-publication this week of a cartoon of the Prophet Muhammad.
(John McConnico/Associated Press)

Some observers said immigrant youths were protesting against alleged police harassment as well as the reprinting of a controversial cartoon depicting the Prophet Muhammad.

On Wednesday, more than a dozen Danish newspapers reprinted the Muhammad cartoon, which sparked sometimes violent protests in Muslim countries two years ago.

They called it a gesture of solidarity after police alleged they had uncovered a plan to kill the cartoonist.

The reprinting sparked more protests. In Pakistan, hundreds of demonstrators set fire to Danish flags on Friday and demanded the Danish ambassador's expulsion.

Also on Friday, members of the Muslim community in Copenhagen held a peaceful rally to protest against the re-publication of the cartoon.

Imam Mostafa Chendid of the Islamic Faith Community Centre urged youth to calm down and stop the burning of cars and property, saying it was hurting the image of Islam.

The newspaper Jyllands-Posten originally published 12 cartoons in September 2006 with an accompanying text saying it was challenging self-censorship among artists afraid to offend Islam.

The drawings were later reprinted in other Western media, mostly in Europe, in the name of free speech and news value.