Islamabad, July 28 - Arrested radical cleric Sufi Muhammad, who had brokered a controversial peace deal between the Taliban and the government in Pakistan's restive northwest, is being probed for the extent of his links with the militants, the provincial chief minister said Tuesday.

Interrogators are probing into the depth of the cleric's contacts with the militants and his role in terror acts, North West Frontier Province Chief Minister Amir Khan Hoti told Voice of America.

Once formal charges are filed against Sufi Mohammad, there would be no need for any witness against him as he has publicly issued statements against the constitution, the judiciary and other institutions of the country, Hoti added.

The cleric, who had brokered the Feb 16 peace deal between the NWFP government and the Taliban, was arrested from provincial capital Peshawar for speaking against the government and encouraging violence and terrorism, an official said.

His sons Ziaullah and Rizwanullah were also held.

'Sufi Muhammad criticised the country's judicial system, supported terrorism and his policy strengthened the Taliban after the peace deal in Swat,' NWFP Information Minister Iftikhar Hussain was quoted as saying of the founder of banned militant group Tehreek Nifaz-e-Shariat-e-Muhammadi (TNSM).

'We will not allow anyone to spread terrorism in Swat again and the government will frame terrorism charges against the TNSM chief,' Hussain added.