Britain’s busiest airport Heathrow has been put on high terror alert after "credible" intelligence emerged that al-Qaeda is plotting attacks on airlines flying out of London with the help of women suicide bombers with explosives concealed in breast implants.

 Security checks have been beefed up after intelligence reports surfaced that al-Qaeda is plotting attacks on airlines flying out of London, British media has reported.

"There are genuine fears over this. We have been told to pay particular attention to females who may have concealed hidden explosives in their breasts. This is particularly difficult for us to pick up but we are on a very high state of alert," an airport staff member was quoted by the daily as saying.

 "It's led to long queues here at Heathrow, much longer than usual at this time of the year. But because it's the summer holiday season, no one has complained," the staff member said.

Al-Qaeda's chief bomb-maker Ibrahim al-Asiri is understood to have developed the method of foiling airport scanners by concealing explosives in an implant or bodily cavity, the report said.

It is also feared there is no shortage of volunteers willing to take part in an atrocity after hundreds of extremists recently escaped from prison in Pakistan, it said.

Specialists suggest that breast implant bombs could be set off by injecting another liquid. "Both are very difficult to pick up with current technology and they are petrified al-Qaeda are a step ahead here. It's pretty top secret and potentially very grisly and ghastly," the expert said.