Pakistani President Pervez Musharraf has ordered a crackdown on militant Islamic activities in the country as part of an anti-terrorism drive.
Pakistan has been at the forefront of the war on terror
Gen Musharraf called for tough action, including the removal from markets of publications inciting hatred.
Earlier, the president pledged to help the UK probe into the London bombings.
Pakistan's education minister meanwhile has said there may be some Islamic schools in the country that the government knows nothing about.
He was speaking after Pakistani sources confirmed that one of the London bombers had been in Pakistan.
The bomber, Shehzad Tanweer, is said to have attended an Islamic school there.
'Menace of terrorism'
Announcing the crackdown on illegal Islamic activity, Gen Musharraf said the government "would not tolerate extremism and would continue to combat the menace of terrorism with unflinching determination and force", the Associated Press of Pakistan reported.
Gen Musharraf was speaking at an unprecedented meeting of the country's district police chiefs.
The BBC's Aamer Ahmed Khan in Karachi says the reason Gen Musharraf called the meeting is not clear.
But he says if it was a response to the links between the London bombers and Pakistan, it may result in the security forces covering fresh ground in their anti-terror efforts.
Gen Musharraf ordered security forces to take action, including stopping militant groups collecting donations or displaying arms, and the removal of "hate" material - either in literature or on CDs - from markets by December this year.
Anyone caught engaging in these activities would be "strictly dealt with in accordance with the law", APP quoted Gen Musharraf as saying.
The order came hours after Gen Musharraf pledged his "fullest support and assistance" in Britain's investigation into the London bombings.
Three of the bombers were Britons of Pakistani origin.
The BBC's Paul Anderson in Islamabad reports that Pakistani intelligence and investigation agencies are working flat out to accommodate British demands for leads on any of the bombers of Pakistani descent.
Shehzad Tanweer's family said that he attended a madrassa (Islamic school) for two months in the Pakistani city of Lahore.
Pakistani officials say that so far they have not been able to pinpoint Tanweer's movements in the country or say who he met.
Pakistan has confirmed that one bomber entered the country
They say he entered Pakistan on two occasions legally. There is no record of the entry of the other two bombers entering the country.
Our correspondent says that if they did enter Pakistan after 2002 - when a tracking system which photographed every legal visitor to the country was introduced - they did so illegally.
In an interview with the BBC, Pakistan Education Minister Javed Ashraf said madrassas in the cities were being monitored.
"But those that are in the border belt and on the mountains along the foreign borders... it is very difficult because these are neither registered, nor declared," he told the World Today programme.
"And it is quite possible that there may be some madrassas which are still around about which we do not really have much knowledge," he said.
He urged the British authorities to reveal the name and location of the school attended by the London suspect so that it could be investigated.
UK Foreign Secretary Jack Straw said on Thursday that he was worried about some of Pakistan's madrassas.