A Nato air strike has hit two Afghan military checkpoints in a restive province east of the capital Kabul, killing seven Afghan troops in what an official described as an accident due to bad co-ordination.

Afghan president Ashraf Ghani expressed his "profound sorrow" over the tragedy and ordered an investigation.

The incident happened as coalition helicopters were flying over an area in Logar province where clashes were under way between Afghan troops and Taliban fighters, the Afghan defence ministry said.

Insurgents fired towards the helicopters, prompting a response that destroyed one army checkpoint, the ministry statement added. An unspecified number of the army members were "killed and wounded", the ministry said.

Logar provincial army commander Abdul Razaq said the early morning strike took place in the district of Baraki Barak, about 30 miles east of Kabul.

Mr Razaq revised an earlier higher death toll down and said seven troops were killed and five wounded in the strike.

District governor Mohammad Rahim Amin said the Nato air strike was "likely a mistake, due to bad co-ordination" in an area where Taliban insurgents are highly active.

A US military spokesman in Afghanistan, Col Brian Tribus, said the coalition is aware of an incident in Logar and is investigating.

According to a statement from Mr Ghani's office, the Afghan president appointed a team to "comprehensively probe the incident and come up with clarification surrounding the air strike".

Mr Ghani also urged the international forces to "take maximum precautions" not to harm Afghan civilians and troops in their future operations.

AP