A coalition helicopter crashed in eastern Afghanistan on Sunday, killing two on board.

The helicopter crashed in the Sabari district of the eastern province of Khost, according to eyewitnesses. Khost, which borders Pakistan, is a Taliban stronghold and sits along important insurgent supply routes.

The crash's cause is being investigated, NATO said, adding that there were no reports of insurgent activity in the area at the time.

The coalition declined to release other details about the crash, including the nationalities of those killed.

In southern Afghanistan, an insurgent attack killed a NATO service member Sunday morning, the coalition said.

The coalition declined to release other information about the attack until relatives could be notified.

More than 200 NATO troops have died so far this year in Afghanistan, many of them in the southern provinces where Taliban fighters are trying to regain territory lost over the winter.

In other violence Sunday, a bomb killed two Afghan security guards near the entrance of a Kabul Bank branch in the Maidan Shahr district of Wardak province in central Afghanistan, according to the Interior Ministry.

The explosion occurred as government employees queued up to receive their monthly salaries, said Shahidullah Shahid, a spokesman for the provincial governor.

Also Sunday, a roadside bomb killed an Afghan policeman and wounded three civilians in the restive southern province of Kandahar, said Haji Abdulghani, district governor of Spin Boldak.

In the eastern province of Nangahar, at least two Taliban gunmen shot to death a local counterterrorism official in the Khogyani district Saturday night, said provincial spokesman Ahmadzai Abdulzai.

The Taliban has been waging an assassination campaign against Afghan government and security officials in an effort to undermine the government and to intimidate perceived collaborators.