Pakistani police used tear gas and water cannon in clashes with stone-throwing Islamist protesters on Saturday, as they moved to clear a protest by the religious hardliners who have blocked main routes into Islamabad for more than two weeks.

Clashes immediately broke out between members of Tehreek-e-Labaik, a hardline Islamist party, and some 4,000 police sent to break up the protest camp, police official Saood Tirmizi said.

“Police used water cannons initially and now are firing tear-gas shells at the protesters,” Tirmizi said.

He said dozens of protesters had been taken into custody.

Television footage showed smoke billowing and fires burning in the streets as officers in heavy riot gear advanced.

“We are in our thousands. We will not leave. We will fight until end,” Tehreek-e-Labaik party spokesman Ejaz Ashrafi told Reuters by telephone from the scene.

The protesters have paralyzed daily life in the capital, and have defied court orders to disband, demanding that the minister of law fired.

Tehreek-e-Labaik blames the minister, Zahid Hamid, for changes to an electoral oath that it says amounts to blasphemy. The government puts the issue down to a clerical error.

Pakistan’s blasphemy law has become a lightning rod for Islamists, especially since 2011 when the liberal governor of Punjab province, Salman Taseer, was murdered by a bodyguard for questioning the law that mandates the death penalty for insulting Islam or the Prophet Muhammad.

Tehreek-e-Labaik considers Taseer’s killer, who was executed for murder last year, a hero of Islam.

Fearing violence, the government has blocked several roads with shipping containers to corral the protesters, but that has caused hours-long traffic jams in and around the capital.

The government had tried to negotiate an end to the sit-in, fearing violence during a crackdown.

In 2007, a confrontation between authorities and supporters of radical preachers at an Islamabad mosque led to the death of more than 100 people.