A US major general has reportedly been killed and 15 other people have been wounded after a man dressed in an Afghan army uniform opened fire with a machine gun at the British-run army base known as “Sandhurst in the sand”.

The victims of the attack included both local and Nato forces, a spokesperson for Afghanistan’s defence ministry said, while the German military said those injured included one of its brigadier generals.

The incident occurred at Camp Qargha, a British military training academy located outside the Afghan capital Kabul.

US officials confirmed that one American had been killed and that “about a dozen” of the wounded were also from the US, but declined to comment further. However US media reports said he was Major General Harold Greene, a senior officer with the international military command ISAF.

US military officials said he was the most senior American official killed in action overseas since the Vietnam war.

Afghan military spokesperson General Mohammad Zahir Azimi described the shooter as a “terrorist in an army uniform”, who was killed when soldiers returned fire. He said that three Afghan army officers were among those wounded.

Video: Afghanistan base shooting

Camp Qargha is known as “Sandhurst in the sand” because it was built and its training regime designed on the example of the famous Berkshire academy for officers.

It first took on cadets last October, the BBC reported, and will be the only British military presence remaining in Afghanistan when operations end this year.

Commenting on the attack today, the MoD issued a statement saying it was investigating the incident but that it would be “inappropriate to comment further at this time”.

Nato has also launched an investigation, while the Afghan President Hamid Karzai condemned the shooting as “cowardly”.

In a statement, Karzai said it was “an act by the enemies who don't want to see Afghanistan have strong institutions.”

The shooting comes after a series of protests against the civilian casualties of ongoing Nato operations in Afghanistan. On Tuesday, a Nato helicopter strike targeting missile-launching Taliban militants killed four civilians in the west of the country.