Police in Pakistan have detained about 200 suspected Islamist extremists in a series of raids on religious schools, mosques and other properties.
Islamabad students outside their seminary after a raid
Most belong to banned militant groups and are wanted "in terrorist cases", Interior Minister Aftab Sherpao said.
The crackdown comes after London bombs killed at least 56. Three of the four bombers visited Pakistan last year, but it is not clear they met militants.
Pakistan's main Islamic opposition says dozens of its members have been held.
On Tuesday, British Prime Minister Tony Blair said he was anxious for Pakistan to crack down on extremist teaching in its Islamic schools.
One overnight raid was on a prominent Islamic school, or madrassa, in Islamabad.
Known as the Lal Masjid, the mosque and its adjacent religious school are known for supporting a banned extremist group, the BBC's Zaffar Abbas reports from Islamabad.
Armed police entered the school and took away two senior clerics and more than 15 students.
Hundreds of students protested before riot police dispersed them with tear gas.
As well as raids in the capital, more than 80 people were rounded up in raids in three cities in Punjab province, security officials told the BBC. None of them have been formally charged.
In North-West Frontier Province, police detained 40 suspects, said to be members of banned militant groups. Thirty-five arrests were made in Sindh province, and another 35 in Balochistan, officials said.
A senior security official told the BBC one of the main purposes of the raids was to find possible clues about the movements of two of the London bombers who travelled to Pakistan last year.
But Information Minister Sheikh Rashid Ahmed denied that among those detained was a British Muslim wanted in connection with the London bombings.
Gen Musharraf is expected to announce new measures
"The person arrested is not the al-Qaeda suspect... he is not the al-Qaeda man as reported by the media," he told the BBC.
Reports that a man "with direct links" to the London attacks had been held in Lahore could also not be confirmed.
Pakistan's Islamic opposition alliance challenged the official view that most detainees were militants.
It said its members had been rounded up across the country, and accused President Pervez Musharraf of acting under pressure from Tony Blair.
Speaking in London, where he was to lay a wreath for an Afghan killed in the bombings, Afghan President Hamid Karzai said those who commit terrorism in the name of Islam are not real Muslims.
He called on Pakistan to close down some madrassas, which he described as terrorist training camps rather than religious schools.
The latest raids, in which Islamist publications have also been targeted, follow crackdowns launched in 2000 and 2002.
These proved to be effective for only a short time, as militant groups re-emerged with new names.
President Musharraf has said he will extend full support to Britain in the investigation into the London suicide attacks.
Pakistan has confirmed that three of the bombers, all Britons of Pakistani descent, visited the country in the last year. The family of one, Shehzad Tanweer, say he visited a madrassa.
Pakistan's ambassador to Britain, Maleeha Lodhi, told the BBC the bombers' motivation "appeared to be home-grown".
"Just a visit to a country doesn't mean that they have been radicalised," she said.
President Musharraf is expected to announce new measures to curb religious extremism on Thursday.