More than two dozen suspects were detained in Punjab province on Tuesday in a series of raids linked to investigations into the London attacks, which killed 56 people, including the four suspected bombers.
Officials say three of the bombers, British Muslims of Pakistani descent, entered Pakistan through the southern city of Karachi last year.
They say at least one visited Islamic schools or madrassas, some of which are seen as breeding grounds for fighters.
Security forces raided religious schools and offices across the country after Musharraf issued "clear orders" to stop the spread of violence and hatred, a top official monitoring the operation said.
"This crackdown is aimed at eliminating a network of nurseries (madrassas) where militants, including those coming from outside, get ready-made facilities for grooming and training," the official added.
British Prime Minister Tony Blair on Tuesday said he was "anxious" for Pakistan to crack down on the madrassas where extremist views might be taught.
"Launching bomb attacks in London in the name of Islam is not Islam"
President Pervez Musharraf
Police went into action after Musharraf held a meeting with top civil and military intelligence officials on Monday to give his approval for the campaign, the official said.
Call against extremism
A key ally in the US-led "war on terror", Musharraf will make his address on state-run television and radio on Thursday evening, said a senior government official, who asked not to be identified.
"It will be an important speech. It will focus on extremism and the London attacks," another government official said.
At a conference in Islamabad on Monday, the Pakistani leader said the nation had to reject extremism.
"Stand up and launch a jihad against extremism - and jihad for peace, brotherhood and unity in the society," Musharraf said. "Launching bomb attacks in London in the name of Islam is not Islam."