Five military personnel killed when the UK helicopter they were travelling in crashed in southern Afghanistan are feared to be British.
The Ministry of Defence said it was investigating the circumstances of the crash but could not confirm the nationality of the troops who were killed.
But sources said it is believed that they were British and the process of contacting next of kin is under way.
The crash, which makes this the bloodiest day for foreign troops in Afghanistan in 2014, is not thought to have involved any enemy action.
An MoD spokesman said: “We can confirm that a UK helicopter crashed in southern Afghanistan today.
“The incident is under investigation and it would be inappropriate to comment further until families have been notified.”
Today’s deaths bring the total number of international troops killed in Afghanistan this month to seven.
Nato forces are currently preparing to withdraw combat troops by the end of this year, with responsibility for fighting the Taliban insurgency handed over to the Afghan army and police.