WASHINGTON (AP) — Afghan President Hamid Karzai on Thursday condemned a video depicting what appears to be four U.S. Marines urinating on the corpses of Taliban fighters.

A presidential statement described the act as “completely inhumane” and called on the U.S. military to punish the Marines.

The Marine Corps said Wednesday it is investigating the YouTube video but has not yet verified its origin or authenticity. The case has being referred to the Naval Criminal Investigative Service, the Navy’s worldwide law enforcement organisation.

The Afghan Ministry of Defense also condemned the actions in the video, which it described as “shocking.”

The NATO-led security force in Afghanistan released a statement Thursday saying, “This disrespectful act is inexplicable and not in keeping with the high moral standards we expect of coalition forces.”

The International Security Assistance Force said the actions “appear to have been conducted by a small group of U.S. individuals, who apparently are no longer serving in Afghanistan.” The statement did not identify the personnel or explain why the ISAF thought they had left the country.

Sen. John McCain, a Navy veteran who fought in the Vietnam war, said the incident “makes me so sad.”

McCain, the top Republican on the Senate Armed Services Committee, called the Marine Corps one of America’s strongest institutions and said its image has apparently been tarnished by “a handful of obviously undisciplined people.”