ISIS plan to attack SAS troops in Syria with suicide bombs in bras.
The fanatics are wiring the garments with plastic explosives in a bid to kill coalition troops.
The tactic means women suicide bombers can show their midriffs if searched without revealing the bombs.
It is understood one was found in Afrin, northern Syria, in April. It is now believed the bras are being produced by highly skilled operatives.
A security source said: “It’s just another example of the inventiveness and determination these people possess to kill.
“It’s a close proximity weapon. They are a small, lightweight device but can be lined with enough plastic explosive to kill everything standing within a 10-metre radius.
“It’s an ideal weapon for a checkpoint approach.”
The UK has never made public the number of special forces it has operating in Syria but it is thought to be dozens.
In 2007 a Tamil Tiger suicide bomber used a bra bomb to blow herself up outside the offices of a minister and ended up killing a secretary.
It is also suspected that a similar device was used in the assassination of Indian Prime Minister Rajiv Gandhi by the Liberation Tigers of Tamil Eelam in 1991.
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