According media reports at least six people were killed on the previous day, when several thousand police and paramilitary tried to disperse a sit-in protest by the religious hardliners, who have blocked the main route into the capital from the neighbouring garrison city of Rawalpindi.
More than 125 people were wounded in Saturday's failed crackdown, and police superintendent Amir Niazi said 80 members of the security forces were among the casualties.
On Sunday morning, smoke billowed from the charred remains of a car and three motorcycles near the protest camp, where several thousand members of the Tehreek-e-Labaid party have gathered in defiance.
"We will move when we have orders," Niazi, the police superintendent, said on Saturday. "What the protesters did yesterday was in no means was lawful. They attacked our forces."
Activists from Tehreek-e-Labaik have blocked the main road into the capital for two weeks, accusing the law minister of blasphemy against Islam and demanding his dismissal and arrest.
While hardliner parties are unlikely to win a majority they could play a major role in elections that must be held by summer next year.
Tehreek-e-Laibak was born out of a protest movement lionizing Mumtaz Qadri, a bodyguard of the governor of Punjab province who gunned down his boss in 2011 over his call to reform strict blasphemy laws.
The party won a surprisingly strong 7.6 per cent of the vote in a by-election in Peshawar last month.
(Writing by Kay Johnson; Editing by Simon Cameron-Moore)