Rehman Malik, Pakistan's interior minister, said two "high-value targets" were among those seized in the raid, but gave no names.
Another official said: "We have reasons to believe that we got the right man who had played a role in the 2005 attacks in London."
Local officials in Pakistan said the raid stemmed from a tip-off from US intelligence officials, who witnessed the operation but did not take part in it.
"It was a well-planned raid carried out against a militant den. The culprits were caught off guard and captured without resistance," a senior Pakistani security official said.
The British foreign office said it was investigating the reports of the al-Qaeda operative's arrest.
In the July 7, 2005, bombings, four young British men killed 52 people and wounded hundreds when they carried out suicide bombings on three underground trains and a bus in central London.
At least two of the men were known to have travelled to Pakistan, where investigators believe they made contact with armed groups.
Last month, Gordon Brown, the British prime minister, pledged £6m ($9m) to help Pakistan tackle militancy.
Britain says it has a vested interest in trying to help Islamabad, as the majority of "terror plots" investigated by British authorities in London have links to Pakistan.