Seven suspected militants have been arrested during a raid near Pakistan's north-western city of Peshawar, officials say.
Pakistani security officials told the BBC they suspect some of the men are members of al-Qaeda.
The men were detained on Wednesday during an operation in the Bara area near Peshawar.
Unconfirmed reports say one of the men could be linked to the 7 July, 2005 London bombings.
A UK Foreign Office spokesman said: "We are investigating the reports."
Fifty-two people were killed and more than 700 injured in a series of suicide attacks on London's transport system.
Unnamed intelligence officials were quoted by the Associated Press and Reuters news agencies as saying that the raid on the house of an Afghan refugee on the outskirts of Peshawar stemmed from a tip from US officials.
The officials said the men were believed to have planned attacks on convoys of trucks carrying supplies to Western forces in Afghanistan.
Two or three of the arrested persons are said to be ethnic Arabs, while the rest are Afghans, says the BBC's M Ilyas Khan in Islamabad.
A resident of Bara Qadeem village where the raid took place told Reuters that he saw some "goras" - a term usually used in the South Asian subcontinent to refer to white-skinned Westerners - observing the raid.
"They came in a black car with tinted glass, but did not take part in the operation," the man said.
The four suicide bombings on three underground trains and a bus in central London in July 2005 killed 52 people and injured about 800.
Earlier this month, US and Pakistani sources said that al-Qaeda's operations chief in Pakistan and another top aide had been killed by a missile fired from a US drone near the Afghan border.
One of them, Usama al-Kini from Kenya, was believed to be behind last year's deadly attack on the Marriott hotel in Islamabad, US officials said.
Fifty-five people were killed when a truck packed with explosives rammed the hotel in September 2008.
The US has launched dozens of similar drone attacks in recent months, mostly targeting Taleban and al-Qaeda militants in Pakistan's tribal regions.
The lawless tribal areas (Fata) on Pakistan's border with Afghanistan are considered a sanctuary for the insurgents.
The US says the militants regularly cross over the porous border into Afghanistan where the US troops have been fighting since 2001.
US President Barack Obama has said in the past that he would use military force if necessary against al-Qaeda in Pakistan even without Pakistan's consent.
Pakistan's foreign ministry has maintained that any threat to act against al-Qaeda from within its territory should not be used for political point-scoring.