LAHORE: Police in Pakistan said a extremist Islamist group had taken six security personnel hostage at its headquarters in Lahore on Sunday after a week of violent clashes following the arrest of the group's leader.

The Tehrik-i-Labaik Pakistan (TLP) group had given the government an April 20 deadline to expel the French ambassador over the publication of cartoons in France depicting the Prophet Mohammad. The authorities responded by arresting its leader, prompting supporters to hold protests and sit-ins across Pakistan. At least four people were killed, hundreds injured, and thousands arrested. Pakistan banned the group after the violence.

A senior police officer and two paramilitary were among the six being held by supporters of (TLP), Lahore police spokesman Arif Rana told Reuters.

"The TLP activists have two fuel tankers containing thousands of liters of petrol. They are throwing petrol bombs and stones at security officials, and also shooting bullets as the result of which 11 officials are injured," Rana said, adding the operation was ongoing.

TLP spokesman Shafiq Amini told Reuters four supporters had been killed on Sunday by police and several others were wounded.

Pakistani news channels have been barred from providing coverage of the group since it was banned last week , and on Sunday mobile and internet services were down in the area where clashes were taking place.

Roads leading to the headquarters of the group, in Lahore's Chowk Yateemkahan, have been blocked.

Still, supporters of TLP have been sharing videos on social media of what they said were clashes on Sunday with police, and hashtags supporting the group were trending in Pakistan on Sunday.

The videos, which Reuters could not independently verify, showed thousands of protesters clashing with police in riot-gear, as clouds of tear gas hung in the air and the crackle of gunfire could be heard. Other videos showed injured protesters being carried away.

On Saturday Prime Minister Imran Khan said the group had been banned because it "challenged the writ of the state and used street violence & attacking the public & law enforcers."

Last week France advised its citizens to temporarily leave Pakistan for their safety.