Two Afghan policemen also died and two others were wounded in yesterday''s explosion in the mountainous Shorabak district of Kandahar province, 19 kilometers from the Pakistan border, said General Abdul Raziq, chief of the Afghan border police in the province.
"Two months ago, we cleared this area of terrorists, but still they are active there," Raziq said.
The Taliban claimed responsibility for the blast.
"A bomb was planted for them in a field," Taliban spokesman Qari Yousef Ahmadi told The Associated Press in a telephone call.
A US official, speaking on condition of anonymity because he was not authorised to disclose the information, confirmed that seven American service members died in the bombing.
The international military coalition reported that one additional NATO service member was killed yesterday when a helicopter crashed in the east.
US officials said seven American soldiers were killed in the bombing. NATO said an eighth soldier was also killed, but his nationality was not immediately released.
It was the deadliest day for coalition forces in Afghanistan since April 27, when a veteran Afghan military pilot opened fire at Kabul airport and killed eight US troops and an American civilian contractor.