Thousands of Islamists blocked highways and rail tracks and clashed with police in different parts of Pakistan in protest against the arrest of their leader ahead of rallies denouncing French cartoons depicting the Prophet Mohammad, officials said.

The blockades have paralysed business in almost all major cities.

Police fired tear gas to disperse the protesters, government official Naveed Zaman said, adding that they had refused to leave until the release of their leader, Saad Rizvi, who was arrested on Monday.

"The protesters started blocking highways, and main entry, exit routes to major cities late on Monday," Zaman told Reuters, adding they attacked and wounded several police and damaged public vehicles.

Rizvi is the head of an extremist group, Tehrik-i-Labaik Pakistan (TLP), that rose to prominence making the denunciation of blasphemy against Islam its rallying cry.

The blockades caused hours of traffic jams and the Islamists were regrouping on Tuesday, government spokeswoman Firdaus Ashiq Awan told Reuters.

The group blocked one of the main roads into the capital late last year and called off their protest only after the government signed a deal with them, agreeing to endorse a boycott of French products.

At the time, protests had broken out in several Muslim countries over France's response to a deadly attack on a teacher who showed cartoons mocking the Prophet Mohammad to pupils during a civics lesson.

Pakistan's parliament had condemned the re-printing of the cartoons in France, urging the government to withdraw its ambassador.

For Muslims, depictions of the Prophet are blasphemous.

The agreement was revised earlier this year to extend the deadline for a parliament resolution to expel the French envoy until April 20 when the group had plans to hold countrywide rallies.

Police arrested Rizvi ahead of the rallies.

"We are out on the streets because the government didn't honour the agreement," said the group's spokesman, Ejaz Ashrafi.

The French embassy in Islamabad and Pakistan's foreign ministry did not respond to a request for comment.