The U.S. military started Wednesday verifying the origin and authenticity of a video clip showing its marines urinating on three slain Taliban fighters.

An official with the U.S. Marine Corps, speaking on condition of anonymity, said Thursday two of the four marines in the video have been identified, according to AP and DPA.

The 40-second clip can be seen at http://www.marinecorpstimes.com/news/2012/01/marine-allegedly-urinates-on-corpse-in-video-011112/.

A YouTube user with the nickname semperfiLoneVoice first uploaded the clip on the popular video-sharing site on Tuesday. The uploader of the clip put a caption beneath the video identifying the urinating men as members of a scout sniper team assigned to 3rd Battalion, 2nd Marines, out of Camp Lejeune, North Carolina.

Capt. Scott Sasser, a spokesman for the battalion's parent command, II Marine Expeditionary Force, on Tuesday declined to confirm if men from the 3rd Battalion, 2nd Marines were the ones on the video clip. The unit returned to Camp Lejenue in October after seven months of engagement with Taliban insurgents in Afghanistan's Helmand province.

Capt. Kendra Hardesty, a Marine spokeswoman at the Pentagon, said Wednesday that Marines officials are working to confirm the men's unit and their identities, according to Marines Corps Times. Once the identities are established, an investigation will follow, she said.

The video clip spreading on the Internet has incensed Afghan President Hamid Karzai, who demanded the punishment of the American soldiers for desecrating dead bodies of Afghans.

"This act by American soldiers is simply inhuman and condemnable in the strongest possible terms. We expressly ask the US government to urgently investigate the video and apply the most severe punishment to anyone found guilty in this crime," said Karzai in a statement.

The U.S. Marines Corps and even the NATO-led International Security Assistance Force (ISAF) in Afghanistan expressed disappointment over the actions of the American soldiers.

"The actions portrayed are not consistent with our core values and are not indicative of the character of the Marines in our Corps," a statement from the U.S. Marine Corps said.

"This behaviour dishonours the sacrifices and core values of every service member representing the 50 nations of the coalition," ISAF said in a statement.

U.S. Defense Department spokesman, Navy Capt. John Kirby, described the image as "disgusting."

Taliban spokesman Zabihullah Mujahid said they have seen similar American brutality before. Mujahid, however, said the clip will not affect talks or a prisoners swap between the insurgents and Western occupiers.

Kabul merchant Qaisullah told AFP the video will cause demonstrations against the U.S. in Afghanistan and the world. Another Afghan told the news agency that the Marines committed a crime and foreigners in the country should leave.

Most online comments on the video were criticisms against the U.S. Marines. U.S. Marines, however, expressed approval of their colleagues' actions on the Marine Corps Times' Facebook page. One reader posted a message saying, "I'd do the same and all my grunt brothers would too."

There are about 20,000 U.S. Marines in Afghanistan, mostly deployed in the southern provinces of Kandahar and Helmand.