Pakistani Interior Minister Rehman Malik has threatened action to end a protest near the country's parliament.
Followers of the charismatic cleric Tahirul Qadri are demanding the resignation of the government.
Mr Malik said the cleric and his followers were at risk from militant attacks and would be held responsible for any bloodshed.
On Tuesday the Supreme Court ordered the arrest of PM Raja Pervez Ashraf over corruption allegations.
Mr Ashraf denies accepting bribes when approving power generation projects as minister for water and power in 2010.
Analysts say that the move is unlikely to lead to his immediate removal.
Mr Malik said action to end the protest was "on the cards" but did not specify what would be done or when.
He said Mr Qadri was in a bomb-proof container, but had refused to heed fresh warnings about possible attacks on him and his followers.
A medical board was being established to examine Mr Qadri's mental health, Mr Malik added.
President Asif Ali Zardari has said the government wants to end the mass protest through negotiations, not force.
Mr Qadri's march from Lahore to the capital culminated in a mass rally on Monday evening.
Clashes briefly erupted on Tuesday before Mr Qadri addressed thousands of supporters camped near parliament, vowing to continue his mass protest indefinitely.
The cleric has said he wants the military and judiciary to be involved in installing a caretaker government to oversee the forthcoming elections.
But he suffered a setback on Wednesday when the leader of the main opposition, the Pakistan Muslim League, refused to back his protests.
"Tahirul Qadri is working on somebody's agenda to derail democracy in Pakistan and we reject all of his demands," Nawaz Sharif told journalists.
The BBC's M Ilyas Khan in Islamabad says there has been speculation that Mr Qadri may be fishing for a role for the military and the judiciary when it comes to the appointment of an interim government which will preside over elections, due in May.