Four Afghan civilians have been killed and one injured in an airstrike called in by British forces, the Ministry of Defence said.
It is understood two women and two children died in the incident in Helmand Province on Tuesday.
A spokeswoman said British troops called in air support after being caught in a Taliban ambush at an undisclosed location in the southern part of the war-ravaged province.
The four bodies and one injured person were found as soldiers went to inspect the area.
The MoD said in a statement: "We can confirm UK forces were involved in an operation in the south of Helmand Province.
"We deeply regret that this incident happened and do everything we can to mitigate this from happening.
"This incident is currently under investigation and it would be inappropriate for us to comment."
