ISLAMABAD (AFP) – Pakistani authorities have said they had arrested seven people over a plot to blow up multiple airliners, including two British nationals who were allegedly key players in the terror scheme.

The Britons, both of Pakistani descent, were seized last week and provided vital information that helped to bust the plot while five local militant “facilitators” were arrested separately, officials said Friday.

British Home Secretary John Reid thanked Pakistan for its assistance after the arrests, which Islamabad said were part of a coordinated operation with British and US intelligence.

“One of the suspects was arrested in Karachi and another was arrested in Lahore. Both the men were British nationals of Pakistani origin and were key members of the Britain-based network of militants,” a senior Pakistani government official told AFP on condition of anonymity.

“The arrests in Pakistan were made prior to the action in London. They were in full knowledge of the plot to blow up the airliners and the information was passed on to Britain and US intelligence,” the official added.

Foreign office spokeswoman Tasnim Aslam said Pakistan “played a very important role in uncovering and breaking this international terrorist network. There were some arrests in Pakistan which were coordinated with arrests in the UK.”

Pakistani agents also arrested a network of five domestic extremists in connection with the London plots, a security official said, saying they had acted as “facilitators” for the Britons.

Another security official said late Thursday that at least three of the people arrested in Pakistan had links to Al-Qaeda.

London’s Guardian newspaper quoted a British government source as saying that an intercepted message from Pakistan telling the bombers to “go now” had triggered the arrests.

Pakistan stepped up security at its own airports Friday following Britain’s announcement that it had thwarted a plot to wreak “mass murder” by simultaneous bombings of planes bound for the United States.

Authorities were also investigating some financial transactions made by an unnamed foreign Muslim welfare group to at least a dozen branches of banks in Karachi and northwestern Peshawar city, a security official.

The Bank of England, Britain’s central bank, said Friday it had frozen the accounts of 19 of 24 men arrested in Britain on Thursday over the allegations, and publicly released their names.

Separately ABC News quoting Pakistani officials identified the ringleader of the bomb plot as Matiur Rehman, said to be a 29-year-old Al-Qaeda commander accused of involvement in plots to kill President Pervez Musharraf.

He was said to be missing along with five others, ABC said, adding that Rehman was known to be planning a “terror spectacular” to mark the fifth anniversary of the September 11 attacks in the United States.

Al-Qaeda has already been fingered as a possible culprit behind the plot. Pakistan has arrested dozens of Al-Qaeda militants, including the capture three years ago of Khalid Sheikh Mohammed, the alleged mastermind of 9/11.

But Musharraf has faced international criticism for failing to crack down on militancy, despite surviving three assassination attempts by extremists linked to Al-Qaeda.

Pakistan came under pressure after the July 7, 2005 suicide attacks on the London transport system when it emerged that some of the British-born bombers had attended Islamic religious schools, or madrassas, here.

However Britain’s Reid thanked Pakistan for its help in uncovering the airliner plot.

“We are very grateful for all the help and cooperation we have received from our international partners, including Pakistan, and I would like to thank them for the assistance they have given us,” he told a news conference in London.