Armed men have killed nine Afghan troops close to the border with Pakistan, a provincial government official said.

It was unknown who was behind one of bloodiest attacks on Afghan troops in several months, said Haji Muhammad Wali on Friday, spokesman for the governor of the southern province of Helmand.

The soldiers were ambushed while on night patrol in the remote Chakool Ghar area late on Thursday.

"Two of those killed were officers and the other seven were soldiers," Wali said.

"The car they were travelling and their weapons have gone missing, too."

PHOTO CAPTION

Afghan children play football in the snow in front of the tomb of former Afghan King Nader Shah in Kabul. (AFP/File)