The government is ready for negotiations with Faizabad protesters, a minister said Saturday, as clashes between Tehreek-e-Labaik activists and security forces turned violent.

Interior Minister Ahsan Iqbal said the government launched a crackdown against the protesters on the directives of Islamabad High Court .

"We are trying our best to control the situation with minimum casualties. The option for negotiations is always available," he told the state-run Pakistan Television (PTV).

Police on Saturday used tear gas and watercannon, and fought running battles with stone-throwing Islamist activists, as they moved to clear a sit-in by the religious hard-liners who have blocked the main routes into the capital of Islamabad for more than two weeks.

The protests have spread to other main cities, including Karachi, Lahore, Rawalpindi and Peshawar.

The clashes began when police launched an operation involving some 4,000 officers to disperse around 1,000 activists from Tehreek-e-Labaik, a new hard-line Islamist political party, and break up their camp.

Television footage showed a police vehicle on fire, heavy curtains of smoke and fires burning in the streets as officers in heavy riot gear advanced. Protesters, some wearing gas masks, fought back in scattered battles across empty highways and surrounding neighbourhoods.

By midday, TV coverage had been cut off and private channels were off the air by orders of the official media regulator.

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

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.