Two British air force members have been killed in a helicopter crash in Afghanistan, the Ministry of Defence (MoD) said.
The RAF pair died after a Puma Mk 2 helicopter crashed while landing at Nato's Resolute Support mission headquarters in the Afghan capital Kabul.
They were among five people killed, while five others were injured.
The MoD insisted the crash was an "accident", while an Afghan security guard said the aircraft appeared to strike an observational balloon as it landed.
An MoD spokeswoman said: "The incident is currently under investigation but we can confirm that it was an accident and not the result of insurgent activity.
"The family of the two personnel who were killed have been informed and requested a period of grace before their names are released."
The two British casualties were from 230 and 33 Squadrons, both of which are based at RAF Benson, between Oxford and Reading in south Oxfordshire. The MoD has not released any further details about the victims.
Resolute Support is a Nato-led mission to train and assist Afghan security forces and institutions, following the stand-down of the International Security Assistance Force (Isaf) last year. The MoD said around 500 British troops remain in Afghanistan as part of the mission.
All five people killed in the crash - which happened at around 4.15pm yesterday - were Resolute Support personnel, a spokesman for the mission said.
A US Army spokesman confirmed there had been an incident involving a Nato aircraft and an observational balloon "in the vicinity of the Resolute Support base", in which the balloon was severed from its mooring.
The latest deaths bring the total number of British forces personnel or MoD civilians killed while serving in Afghanistan since the start of operations in October 2001 to 456.
The helicopter crash happened hours after a convoy of UK military vehicles was attacked in Kabul in a separate incident. Three civilians - said to include a woman and a child - were wounded but no-one was killed.
The MoD said the blast was caused by an improvised explosive device and there were no British casualties.
But the Taliban, which claimed responsibility for the attack, and Kabul's police chief said the Nato convoy was targeted by a suicide car bomber.
An MoD spokesman said last night: "We can confirm that at approximately 9.10am this morning a convoy of UK military vehicles on a routine road move, as part of the Nato Resolute Support mission in Kabul, was struck by an improvised explosive device. There were no UK casualties."
Taliban spokesman Zabihullah Mujahid sent a statement to local media claiming responsibility for the explosion.
There have been a number of attacks in Kabul in recent weeks, including an incident on October 6 in which the house of former Helmand governor Nahim Baloch was targeted.