Pakistani police have filed charges against an influential pro-Taliban cleric who helped to broker a controversial peace deal in February between the government and Taliban militants in Pakistan's northwestern Swat Valley.

Swat Police Chief Sajid Mohmand said authorities have accused the hardline religious leader Maulana Sufi Muhammad with aiding terrorism, sedition and conspiring against the government.

The charges come from comments Muhammad made during an April speech, in which he condemned democracy and Pakistan's constitution.  A court is expected to formally charge Muhammad in the coming days.

Authorities arrested Muhammad in Peshawar last Sunday.

Sufi Muhammad is father-in-law of Swat's Taliban leader Maulana Fazlullah.  Muhammad helped to broker the peace deal that required the militants to end their two-year insurgency in exchange for the establishment of strict Islamic law (Sharia) in Swat.

But the truce collapsed in April when the militants pushed out of the Swat Valley and advanced to just 100 kilometers from the capital, Islamabad.

Pakistan's military says more than 1,800 militants have been killed since it launched its offensive in the area after the peace deal collapsed.

On Sunday, the military said its troops killed four militants and captured 28 others, including a local commander, in the latest operations in Swat and Malakand.

Casualty figures given by the military are difficult to verify because journalists do not have access to the war front.  The fighting has displaced nearly two million people.  

Some information for this report was provided by AFP, AP.