An investigation was under way tonight into whether two British servicemen killed in southern Afghanistan died as a result of "friendly fire".
The Ministry of Defence said an inquiry was looking into the whether the two men, who died in an explosion in north-east of Gereshk in central Helmand on Wednesday, were caught up in a so-called "blue-on-blue" incident.
"We have confirmed that an investigation is under way into a suspected friendly fire incident," a MoD spokesman said.
Earlier the men were named as Captain Tom Sawyer, 26, of the Royal Artillery, and Corporal Danny Winter, 28, of the Royal Marines.
The two men died while on a joint operation with Danish forces and the Afghan National Army to clear a known Taliban stronghold. Two other members of their patrol were also injured.
It is understood the suspected friendly fire incident did not involve fast jets or other international forces.
Capt Sawyer, from Hertfordshire, was serving in Helmand as a fire support team commander attached to 45 Commando, Royal Marines.
He had hoped to pursue a career in the special forces, and his superior officers said he would "undoubtedly" have succeeded.
His family - including his wife Katy, whom he married in March last year - said they would always remember him as "our hero".
Capt Sawyer was educated at Watford Grammar and at Rickmansworth School.
He was an Air Training Corps cadet in Watford before joining the Army and being selected for officer training at Sandhurst.
The soldier received a Brigade Commander's Commendation for his service on an earlier tour in Afghanistan, in which he was given command of an Afghanistan National Army outstation.
Capt Sawyer was then assigned to 7 (Sphinx) Commando Battery based in RM Condor, near Arbroath, Scotland.
He was tasked with preparing his unit ahead of its return to Afghanistan in October last year.
A keen sportsman with a passion for outdoor pursuits, he recently organised and led a regimental skiing team to compete at Army level in Austria.
He had planned to take his soldiers adventure training in Cyprus at the end of their tour in Afghanistan.
Comrades paid tribute to his good humour, describing him as "one of life's great characters".
Capt Sawyer is survived by his wife, his parents, Martyn and Susan, and his sister, Wendy.
His family said in a statement: "Tom was the best husband, son and brother we could ever have asked for.
"He deeply loved his family and friends, and his infectious personality touched all those who knew him.
"Dedicated to the Army and his lads, he was loyal, loud and loving.
"He will leave a big hole in all of our lives but will always be remembered as our hero."
Lieutenant Colonel Neil Wilson, commanding officer of 29 Commando Regiment Royal Artillery, said: "Captain Tom Sawyer died a hero, doing a job he loved and whilst taking the fight to the enemy in the only way he knew.
"He was a first-class officer with a natural flair for command and was hugely respected by all his fellow officers and by the soldiers he commanded."
He said the soldier was a "gregarious, fun-loving, universally-popular character" with a ready smile.
Captain Sam Hewitt, fire support team commander with 26 Regiment, Royal Artillery, described Capt Sawyer as a "true friend".
He said: "Tom had an enthusiasm for life paired with an overwhelming kindness which always seemed to brighten up a room.
"He worked hard and possessed a natural ability to lead, gaining respect from the soldiers under his command throughout the Gunners.
"Tom always worked hard for his men and commanded with style and panache. He lived for his family and friends and died doing the job he loved.
"He was an officer in every sense of the word, with qualities such as honour, selflessness and courage in abundance.
"The world will be a sadder place without Tom and I will miss him greatly."
Cpl Winter, who was born near Manchester and lived in Stockport, was a specialist mortar fire controller serving with Zulu company of 45 Commando, Royal Marines.
His role was to provide mortar support to frontline fighting troops.
He joined the Royal Marines in October 1996 and quickly came to specialise in heavy weapons.
Serving with both 40 Commando and 45 Commando, Cpl Winter was deployed on operations in Northern Ireland and in southern Iraq at the start of the war in 2003.
Friends described him as a loyal and dedicated Royal Marine who "worked hard and played even harder".
A passionate Manchester United fan, he leaves behind his partner, Amanda.
Lieutenant Colonel Jim Morris, commanding officer of 45 Commando group, said Cpl Winter was an "exceptional" Royal Marine with a big future ahead of him.
He said: "Brave, committed, extremely determined and operationally experienced, he had a gift for giving honest advice and opinion without raising hackles and he was tremendously well respected by all ranks as a result.
"He was killed right at the forefront of an operation whilst providing the measured and balanced advice to his commander that had become his trademark.
"His loss has been deeply felt across the whole of 45 Commando and his ultimate sacrifice will always be remembered."
Colour Sergeant Ross Gunning, second-in-command of the mortar troop, said Cpl Winter was always the centre of attention on a night out.
He said: "He enjoyed karaoke and was often seen with a cigarette and pint in one hand, whilst loosely holding the microphone with the other, and belting out Neil Diamond classics at the top of his voice, often involving everyone else around him to great effect.
"Danny progressed in his career and became an outstanding mortar fire controller.
"This was a job that he put his heart and soul into - like his singing - and excelled at. He was one of the best."
The two deaths took the number of British servicemen and women who have died in Afghanistan since the start of operations in October 2001 to 141.
Defence Secretary John Hutton said: "It was with great sadness that I learnt of the deaths of Captain Tom Sawyer and Corporal Danny Winter, one a proven mentor and leader and the other a non-commissioned officer of great professionalism and experience.
"It is clear from the comments of their colleagues and commanders that they were both brave and committed servicemen, with proud records and bright futures in the military.
"Both died doing jobs they loved and for a cause vitally important to their country. We owe them a debt, and at this sad time our thoughts and prayers are with their loved ones and colleagues."Reuse content