Baghdad, Iraq ? An insurgent group linked to al-Qaida posted a Web video Friday showing what it said was the downing of a U.S. military helicopter this week. Seven Americans were killed in the crash.

The U.S. military has said it did not believe the CH-46 Sea Knight helicopter was shot down in the crash Wednesday northwest of Baghdad.

But a U.S. official, who was not authorized to address the topic publicly and spoke on condition of anonymity, said “the video appears to be legitimate” – meaning that it shows a Sea Knight crashing.

The two-minute video – which says it shows the “downing of U.S. aircraft on Feb. 7” – shows a helicopter that appears to be a Sea Knight flying. An object trailing smoke is seen in the sky nearby, and then the craft bursts into orange and red flames, with a spray of debris emerging from it.

It is not clear whether the object is a rocket, and it cannot be clearly seen connecting with the craft.

In the footage, the helicopter heads downward, but appears to be at least partially in control, though smoke and bright flames are trailing from it. The helicopter then disappears behind a line of trees as it hits the ground.

The video was issued by the Islamic State in Iraq, an umbrella group of Iraqi insurgent groups that includes al-Qaida in Iraq. The group on Wednesday issued a written claim of responsibility for the craft’s downing and had promised a video would follow.

The video, titled “the Hell of Christians and Apostates in Iraq,” was posted on a Web forum where the group and other Islamic militants often post messages.

The Islamic State in Iraq has also claimed responsibility for downing two other U.S. helicopters – a Black Hawk which crashed northeast of Baghdad on Jan. 20, killing 12 Americans, and an Apache shot down Feb. 12, in which two U.S. soldiers died.

At least six U.S. helicopters have crashed or been forced down under hostile fire since Jan. 20. In the wake of the recent crashes, U.S. officials have said they were reviewing flight operations and tactics but maintain there is no evidence of sophisticated new weapons used in any of the latest attacks.

The authenticity of Friday’s claim could not be independently confirmed.