Thousands of people rallied in the Pakistani port city of Karachi to protest against Danish cartoons of the Prophet Mohammed and a Dutch film said to insult Islam, police and witnesses said.

"More than 20,000 protesters attended the rally convened by the fundamentalist Jamaat-i-Islami party," a senior police officer Suleman Syed told AFP.

Party leader Munawar Hussain said tens of thousands participated Sunday to vent their anger against the Internet release of a 15-minute film last month by far-right Dutch MP Geert Wilders.

Emotionally charged youths torched Danish and Dutch flags and also chanted slogans against the United States and burned an effigy of US president George W. Bush, witnesses said.

In a resolution the rally urged the government to cease diplomatic ties with Denmark and the Netherlands and expel their envoys.

Witnesses said several other political parties and both Sunni and Shiite Muslims joined the protest.

"Our aim was to send a message to the 57-nation Organisation of Islamic Conference that it should take action in the wake of anti-Islam conspiracies in the West," Hussain said.

The cartoons originally appeared in September 2005, sparking anger and protests across the Muslim world. Five people died in Pakistan in February 2006 during violent protests against the drawings.

At least 17 Danish dailies reprinted one of the cartoons in February, vowing to defend freedom of expression a day after police in Denmark foiled a plot to murder the cartoonist.

The Pakistan foreign ministry last month summoned the Dutch ambassador and lodged a "strong protest" over the film, which it said "deeply offended the sentiments of Muslims all over the world."

"Insult to other religions could never be justified on the basis of freedom of expression," the ministry said in a statement.