At least nine people were killed when a military helicopter crashed in central Afghanistan, the defence ministry said Thursday. 

The crash happened on Wednesday night in a volatile district in Wardak province, where Afghan forces and local militias have bitterly fought. 

"As a result of the incident, four crew members and five security forces" were killed, the MoD said in a statement. 

"The ministry of defense is investigating the cause of the crash."

Mohibullah Sharifi, the spokesman for the Wardak provincial governor, confirmed the helicopter crash, but did not provide further details. 

Helicopter crashes are common in Afghanistan either due to technical problems or militant attacks.

In October last year, nine members of the Afghan military were killed when two army helicopters collided while transporting wounded soldiers in southern Helmand province. 

The Afghan government has been battling a surge in violence across the country blamed on the Taliban, despite supposed peace talks launched between the two sides last year.

In the Afghan capital, four people were killed and nine others were wounded in a blast targeting a bus in east Kabul on Thursday, police said.