A British soldier who died fighting ISIS in Syria was blown up after his US Navy Seal colleague accidentally detonated a grenade, it was revealed today.

Special Air Service Sniper Matt Tonroe, from Manchester, died last year alongside US commando Master Sergeant Jonathan J Dunbar while on an undercover mission to kill extremists.

The 33-year-old - who was embedded in Seal Team 6, the unit which killed Osama Bin Laden - became the first Briton to die fighting terrorists in war-torn Syria.

The Pentagon blamed their deaths on an improvised explosive device (IED) in a statement released days after the incident in March 2018.

But an in-depth investigation into the blast in Manbij, northern Syria, has concluded Sgt Tonroe was killed when a small explosive carried by a colleague, thought to be a grenade, was accidentally detonated.

Forensic tests conducted at the scene failed to locate any IED components, while such a device would also have caused a crater in the ground beneath where Sgt Tonroe and US Master Sergeant Jonathan Dunbar, 36, were found.

Special Air Service Sniper Matt Tonroe, from Manchester, died last year on an undercover mission to kill extremists

US Navy Seal Jonathan J Dunbar was also killed when a grenade was accidentally detonated

A Ministry of Defence spokesman said: 'Sergeant Matt Tonroe died from blast injuries caused by an explosion during a military operation.

'It was initially believed that Sgt Tonroe was killed by enemy action, however subsequent investigation concluded that Sgt Tonroe was killed by the accidental detonation of explosives carried by coalition forces.

'Our thoughts continue to be with Sgt Tonroe's family and friends.'

Following the blast Sgt Tonroe, Master Sgt Dunbar and five other seriously injured casualties were carried on to military vehicles and driven to the outskirts of Manbij, where a medical helicopter was waiting to fly them to a US military hospital at a secret location.

While the evacuation was taking place, US Apache helicopter gunships and US fighter jets armed with air-to-ground missiles flew low over where the explosion occurred to deter jihadis from launching 'follow-up attacks'.

Sgt Tonroe Master Sgt Dunbar were pronounced dead on arrival at hospital.

The Briton's death forced the MoD to concede that UK troops were operating in Syria - something it had previously denied.

The SAS soldier was born in Manchester in August 1984 and joined the Parachute Regiment just days after his 20th birthday.

He passed the Paras’ notoriously tough P Company selection course in 2005 and subsequently joined 3rd Battalion (3 Para).

Sgt Tonroe then passed the Household Division and Parachute Regiment sniper course in October 2007 with flying colours.

He also served as a sniper in Helmand province in Afghanistan in 2008 and was praised for his coolness under fire by colleagues.

It is understood that his sharpshooting accounted for a number of Taliban deaths.

The 33-year-old died last year alongside US commando Master Sergeant Jonathan J Dunbar in the blast in Manbij during the joint mission

According to military sources, Sgt Tonroe was then promoted and attempted SAS selection, which he is said to have passed first time. He was also a fully trained parachutist.

His commanding officer, a Lieutenant Colonel in the Special Forces who cannot be named for security reasons, described Sgt Tonroe as 'a deeply intelligent man and one of life’s characters'.

He added: '‘He was a caring and considerate soul, a loving and dutiful son, and a friend to many.

‘Yet he had a steel core, served his country with pride and was a first-class soldier, proven in combat, faced risk willingly and was ever ready for more.

‘He thus died as he lived: daring and fearless in duty. We mourn his loss dearly, are proud to have known him and will honour him by continuing this fight.’

Sgt Tonroe was survived by his mother Michelle, brother Alex and girlfriend Olivia.

US Special Forces soldier – Master Sergeant Jonathan Dunbar, 36, from Austin, Texas – was also killed when the device exploded near Manbij’s Sheikh Akil cemetery.

Th explosion took place near 'Sheikh Akil graveyard' (pictured) in northern Syria near the border with Turkey

Dunbar was assigned to the headquarters of the US Army Special Operations Command in Fort Bragg, North Carolina.

He grew up in Austin, Texas and joined the Army as an infantryman in 2005, six years after finishing high school, according to USASOC.

Dunbar's first assignment was with 1st Battalion, 325th Airborne Infantry Regiment at Fort Bragg, where he deployed once to Afghanistan and once to Iraq in support of combat operations.

In November 2009, Dunbar transitioned to 2nd Battalion, 38th Cavalry Regiment, a long range surveillance unit, at Fort Hood, Texas. He again deployed to Iraq in support of combat operations.

In 2013, Dunbar was assigned to USASOC, where he served as a team member and deployed three times in support of combat operations in Iraq and Afghanistan.

Dunbar became the fourth American service member to die in Syria since the US began attacking Islamic State group militants there in September 2014.

Manbij, a mixed Arab-Kurdish town, is under threat of a Turkish military operation from across the border.

Ankara says the town is controlled by Syrian Kurdish militiamen that Turkish officials claim are 'terrorists' and an extension of Kurdish insurgents inside Turkey.

The body of a civilian is carried away in a stretcher after an air strike on the town of Ariha, in Idlib province on July 27 - as the war in Syria rumbles on

The development comes on a day that saw government airstrikes kill 11 civilians in the town of Ariha - as the war in Syria rumbles on.

Ariha, in Idlib province, has been particularly targeted over the last week as the government escalates its offensive against the country's last rebel stronghold.

The airstrike also left a three-year old girl with an amputated leg and a man with serious injuries to his bladder and torso.

The Syrian Observatory for Human Rights, which monitors the war, and another activist collective, called Ariha Today, said most of those killed were children. Ariha Today named six children under the age of 14.