KABUL, Afghanistan — Five NATO troops died in a British helicopter crash Saturday in southern Afghanistan, authorities said, the single deadliest day this year for foreign forces as they prepare to withdraw from the country.

The cause of the helicopter crash was not immediately known. Kandahar provincial police spokesman Zia Durrani said the helicopter went down in the province’s Takhta Pul district in the southeast, about 30 miles from the Pakistani border.

The coalition said it was investigating the circumstances of the crash but said it had no reports of enemy activity in the area.

A Taliban spokesman claimed in a text message to journalists that the insurgents shot down the aircraft.

The last deadliest day for coalition forces was Dec. 17, 2013, when a helicopter crash killed six U.S. service members.

Saturday’s deaths bring to seven the number of international troops killed this month.

So far this year, 23 have been killed, according to an Associated Press count, a far lower number than previous years as international troops have pulled back to allowed Afghan security forces to take the lead in security operations.