Armed special forces troops are being deployed on the London Underground and have been told to 'shoot to kill' terrorists.

Members of the SAS and the Special Reconnaissance Regiment have been told to target terrorists who are on trains, buses and planes.

It is believed some of the troops will patrol the busy tube network in the capital in pairs and will be disguised as couples.

They will be armed with Glock 9mm semi-automatic pistols so they can 'take down' potential gunmen and suicide bombers, reports the Daily Star Sunday.

Armed special forces troops (stock photo of SAS soldiers) have been told to 'shoot to kill' after being trained for months

Those in the special covert teams have been trained at the SAS base in Hereford for the past few months.

A source said they are trained in 'rapid-fire techniques' and told the newspaper: 'The task force is comprised of some of the most experienced special forces personnel in the Army.

'The unit is composed of some of both male and female personnel from the Special Reconnaissance Regiment who are trained killers and can pose as couples while travelling on public transport.'

The paper also reports that the trained staff have been given 'soft-nose' bullets to limit the risk of other passengers who are travelling on public transport.

A 'bucket bomb' (pictured) was found inside a shopping bag exploded and injured at least 30 people on Friday

It comes as two men were arrested in connection with the Parsons Green bucket bomb attack which left 30 people injured on Friday.

A teenage suspect, believed to be an Iraqi refugee, was detained in the Port of Dover after being tracked to its departures hall, but it emerged he had been arrested at Parsons Green a fortnight before the blast.

A second suspect, a 21-year-old man, was later arrested in Hounslow, with police also swooping on a house in Stanwell, Surrey, directly opposite Heathrow airport.