A NATO helicopter has crashed in southern Afghanistan, killing the five-member crew and two military passengers -- including a Canadian.

The identity of the Canadian has not been released. The five crew members were American, while the second passenger was British.

The U.S. CH-47 Chinook helicopter went down at about 9 p.m. local time Wednesday in Helmand province, NATO officials said.

A rescue team arriving at the scene was then ambushed by insurgents and had to call in air support to ward off the attackers. One Afghan civilian was injured by gunfire.

Speaking to The Associated Press, supposed spokesperson Qari Yousef Ahmadi said everyone on board the helicopter died when it crashed in Kajaki district.

"We have weapons that we have used to target helicopters before," he told AP.

NATO would only say the cause of the crash was "being determined by military officials."

In recent months, U.S. and British forces have fought against insurgents in Kajaki, where a large hydroelectric dam is being repaired.

The Chinook has two rotors and is mainly used for transport. It can fit about 40 soldiers in addition to a small crew.

Eight U.S. personnel died last February when their Chinook crashed in the southern province of Zabul, but the incident was not the result of a militant attack.

Another 10 U.S. soldiers died in a Chinook crash in May 2006, after an attempted nighttime landing.

But a 2005 U.S. helicopter crash, that killed 16 Americans, is believed to have been caused by a rocket-propelled grenade fired by militants.

With files from The Associated Press