At least eight people have been killed in clashes between Pakistani police and supporters of a prominent Islamic scholar in the city of Lahore.
Dozens more were injured as police fired shots and tear gas to disperse protesters at the offices of Tahirul Qadri. His supporters threw stones.
Two women died in the riots which are now under control, reports say.
Mr Qadri, who is based in Canada, plans to return to Pakistan next week to lead a campaign against corrupt politicians.
He led a "long march" on Islamabad in January last year, but the protest fizzled out with little result.
The BBC's M Ilyas Khan in Islamabad says Mr Qadri is seen by many as a political nuisance who lacks clout.
But he has the ability to gather supporters from his madrassas and is rumoured to have ties with the powerful ISI intelligence agency.
Police in Lahore say clashes broke out after supporters of the Pakistan Awami Tehreek (PAT), which is led by Mr Qadri, resisted attempts to clear barriers outside their leader's offices in the Model Town suburb on Monday night.
When the police brought in reinforcements in the morning, the confrontation grew, although the police insist they showed restraint, the BBC's Mike Wooldridge in Islamabad reports.
A number of arrests have been made.
The Chief Minister of Punjab, Shahbaz Sharif, has ordered a judicial inquiry.
"I am deeply saddened over the killings," Mr Sharif, who is also the brother of Prime Minister Nawaz Sharif, said.
"If I am held responsible, I will immediately resign because I cannot even imagine using force against anyone," he added.
Officials at Lahore's Jinnah Hospital said the bodies of those killed had bullet wounds.
Dr Abdul Rauf told the AFP news agency the hospital had "received 80 injured, 40 with bullet injuries and 40 with other wounds."
Some commentators have criticised the authorities for being heavy-handed in dealing with Mr Qadri's supporters.
They say the barricades had been there for over four years, and had been erected with the consent of the area residents to improve security.
Mr Qadri held a news conference via videolink from Canada to condemn the police raid on his headquarters in Lahore.
He said he remained undaunted and would arrive at Islamabad airport on Monday as planned.
He urged his followers to continue their protest, but remain peaceful and refrain from damaging property.
"The revolution that was to take time in coming will now arrive more quickly," he said. "These deaths will lead to the end of this government."