A majority of the US soldiers who perished in the shooting down of an American chopper in Afghanistan were part of the elite forces that killed Al Qaeda leader Osama bin Laden, a media report said.

Thirty-eight people, including 30 US special forces troops and seven Afghan soldiers, were killed when their Chinook helicopter was brought down Saturday by Afghan insurgents in Wardak province.

Seven members of the Afghan National Army, one dog handler, an interpreter and an unknown number of crew were also on board the downed helicopter.

Of the 30 US troops who died, 22 were Navy SEALs from the elite Team Six unit that killed Osama May 2, the Daily Mail reported.

On Sunday, two names were revealed as victims of the devastating crash. Aaron Carson Vaughn, of Tennessee, was a Navy SEAL and the first special operations soldier to be identified in the devastating crash. The other victim named was another Navy SEAL, Jon Tumilson, of Rockford, Iowa.

Meanwhile, as NATO begins an operation to recover the remains of the large helicopter, an Afghan official said heavy fighting has erupted in the area of the crash.

Wardak provincial spokesman Shahidullah Shahid said Sunday that a joint operation was taking place in the Tangi Joy Zarin area of Sayd Abad district.

He said there were reports of Taliban casualties overnight, but had no additional information.

The SEALs who died in the crash were not among the 23 who killed Osama. According to intelligence officials, the SEALs who killed Osama in Pakistan had recently returned to Afghanistan from their base in North Carolina.

However, they were members of the same 120-strong SEAL Team Six and would have trained alongside and been close friends with those who carried out the Osama raid, the Mail said.

It was not clear if the Taliban had deliberately targeted the helicopter as an act of revenge. But its shooting down is bound to be greeted in the Arab world as terrible vengeance for the death of the Al Qaeda leader, it noted.

The attack is the deadliest single incident since the Afghan war began in 2001.

"A NATO helicopter crashed last (Saturday) night in Wardak province," the Afghan government statement said.

"President Karzai expressed his deep condolences because of this incident and expressed his sympathy to Barack Obama."

Obama, who learned of the incident at Camp David, issued a statement saying his thoughts and prayers go out to the families of those who perished.

"Their deaths are a reminder of the extraordinary sacrifices made by the men and women of our military and their families, including all who have served in Afghanistan," Obama said.

Defence Secretary Leon Panetta said he is deeply saddened by the loss, and vowed that the US will stay the course to complete the mission to make the world a safer place.

The Chinook involved in Friday's attack - a US twin-engined helicopter mainly used to transport troops - was hit by a shoulder-fired grenade as it returned from a night raid on a militant gathering in Tangi Valley, west of Kabul.

The Tangi Valley, dubbed 'Death Valley', is known for being one of the most hostile corridors in Afghanistan. The volatile Wardak province is an infamous insurgent stronghold.

US sources said the troops were being flown by a crew of the 160th Special Operations Aviation Regiment. The Taliban claimed they downed the helicopter with rocket fire and that the wreckage was strewn at the scene.