KABUL, Afghanistan - Eight American troops and a US contractor died Wednesday after an Afghan military pilot opened fire during a meeting at Kabul airport -- the deadliest episode to date of an Afghan turning against his coalition partners, officials said.

An Afghan soldier stands guard outside the Air Force compound in Kabul April 27, 2011. An Afghan Army officer opened fire on foreign troops Wednesday after an argument at the airport in the capital -- the latest in a spate of deadly incidents that have occurred inside government or military installations, the Defense Ministry said. [Photo/Agencies]

The Afghan officer, who was a veteran military pilot, fired on the Americans after an argument, the Afghan Defense Ministry said.

All nine killed were American, according to a senior US defense official, who spoke on condition of anonymity because the information has not yet been made public.

The shooting occurred in an operations room of the Afghan Air Corps at Kabul airport.

"Suddenly, in the middle of the meeting, shooting started," said Afghan Air Corps spokesman Col. Bahader, who uses only one name. "After the shooting started, we saw a number of Afghan army officers and soldiers running out of the building. Some were even throwing themselves out of the windows to get away."

Five Afghan soldiers were injured. At least one Afghan soldier was shot -- in the wrist -- but most of the soldiers suffered broken bones and cuts, Bahader said.

An Afghan pilot who spoke on condition of anonymity, identified the gunman as Ahmad Gul from Tarakhail district of Kabul province.

Dr. Mohammad Hassan Sahibi, the brother of the shooter, who was killed in the incident, had been battling financial troubles. Sahibi said his brother had no ties to insurgents.

"He was 48 years old," Sahibi told Tolo, a private television station in Kabul, "He served his country for years. He loved his people and his country. He had no link with Taliban or al-Qaida.

"He was under economic pressures and recently he sold his house. He was going through a very difficult period of time in his life."

Afghan President Hamid Karzai condemned the shooting and offered his condolences to the relatives of the victims. He said those killed were trainers and advisers for the Afghan air force. The president ordered his defense and security officials to investigate the recent incidents to determine why they occurred.

It was the seventh time so far this year that members of the Afghan security forces, or insurgents impersonating them, have killed coalition soldiers or members of the Afghan security forces.

The Taliban claimed responsibility for the attack. In a statement, Taliban spokesman Zabiullah Mujahid said the gunman was impersonating an army officer and that others at the facility helped him gain access.

However, Defense Ministry spokesman Gen. Mohammad Zahir Azimi said the gunman was an Afghan military pilot of 20 years.

"An argument happened between him and the foreigners and we have to investigate that," Azimi said.