A tribal elder offered Tuesday to allow graves to be opened of people killed in US air strikes in western Afghanistan nearly three weeks ago to prove that most were civilians, many of them children.

Afghan government and UN investigations have backed local claims that more than 90 people were killed in the August 22 strikes but the US-led coalition has said only seven to five civilians were killed along with 30-35 Taliban.

"I declare to the world, I offer them, if you don't believe us, let's open up the graves and see who the dead are," said Gul Ahmad Khan, the elder for the Noorzai tribe in a Herat province village hit in the strikes.

Khan said six of his relatives were killed in his home, which was destroyed by the gunships while he was away at a prayer ceremony. About 76 of the dead were from his tribe, he said.

"You chose the grave, I'll dig it up and show you," he told AFP.

"I swear to God, there were no Taliban among those killed, they were all innocent civilians."

US officials have reportedly cited a lack of physical evidence in their dispute of the claims of more than 90 dead.

Locals says the dead were buried within hours of the early morning strikes. An AFP reporter saw only 22 graves with villagers saying some of the dead were buried together and others buried elsewhere.

Mobile phone and video footage taken by locals soon after the incident has emerged that shows rows of people -- perhaps around 30 -- under blankets in a mosque, including some children.

Some of the footage is of poor quality but it is apparently what has prompted the US military to agree to review its investigation on the request of the most senior US general in Afghanistan, David McKiernon.

A toll of 90 would be one of the deadliest such incidents since the United States led troops into Afghanistan seven years ago to remove the Taliban from government and round up extremist militants.

Human Rights Watch said in a report released Monday that civilian casualties in air strikes nearly tripled from 2006 to 2007, when at least 321 were killed.

In the first seven months of this year, international air strikes had killed at least 119, it said, warning of a public backlash.

The watchdog said a higher number of cases of civilian casualties in air strikes could be attributed to operations by the US-led coalition, also called Operation Enduring Freedom, than to the separate NATO-led force.

This was because the coalition was more active in southern and southeastern areas where the insurgency is strongest, and is reliant on special forces, it said. It also has a different mandate and rules of engagement.

NATO's International Security Assistance Force, commanded by McKiernon, refreshed and reissued guidelines to its troops after the Herat incident in a bid to avoid civilian casualties, a spokesman told AFP.

"We have reissued a tactical directive to continue the improvement of our control measures for the use of air power," Brigadier General Richard Blanchette told AFP.