'Al Qaeda UK linchpin' quizzed

MI5 officers are today quizzing the man suspected of being al Qaeda's most senior UK operative over plans to attack airports and other sites here.

They believe he has been in direct touch with high-ranking al Qaeda suspects in Pakistan and has received information about targets in Britain.

The scale of the suspected network became clear today after surveillance by the intelligence services and Scotland Yard's anti-terrorist squad.

The plot to bomb airports including Heathrow came to light after Pakistani police arrested Mohammed Naeem Noor Khan, the head of Osama bin Laden's secret communications network.

A security source said: "He was involved in planning for attacks at Heathrow Airport some time ago and was wanted by the US government."

Pakistani officials said Khan sent coded orders to the UK contact, who reportedly uses the aliases Abu Eisa or Abu Musa Al Hindi and is codenamed-Bilal. Khan told interrogators after his arrest last month how plans for the attack on Heathrow were sent for Bilal to carry out.

Officials say Khan was in "direct contact" with Bilal over the mission. But only Bilal knew the identities of others who would take part.

Pakistani intelligence would not reveal the timetable or details of how the attack was to be carried out.

But the source said: "What we can say for certain is the plan was drawn up quite recently. Bilal was to execute the plan." Police claimed Tuesday's arrests also foiled a separate plot to car bomb Heathrow or Gatwick, Manchester and Birmingham airports later this month.

An anti-terrorist squad source said: "We're certain there was a conspiracy to carry out a mass attack on airports and made a calculated decision to stop the plot going further." A Scotland Yard official said one of the 12 being questioned at Paddington Green was seen as "a significant figure".

A British Airports Authority spokeswoman said: "We haven't been advised by the police of known links between the arrest and an increased threat to the airport."