It is believed the attack was carried out by an Afghan soldier at the base in northern Afghanistan on Saturday, a military official said.
Abdul Qahar Araam, spokesman for the Afghan Army’s 209th Corps, said: “An Afghan soldier shot and killed four American troops inside the base. We are investigating.”
The US military command in Kabul confirmed it was “aware of an incident” at Camp Shaheen, which is the headquarters of the 209th Corps in the northern city of Mazar-i-Sharif.
But it did not provide more details.
The shooting comes just months after the Taliban carried out a deadly raid on the camp, near the northern city of Mazar-i-Sharif, that killed or wounded dozens people.
Sources suggested as many as 140 people were killed in the attack, which was allegedly in response to the deaths of two Taliban officials in the region.
And last weekened three Americans were killed by an Afghan soldier in Nangahar province.
On Thursday, a Donald Trump administration official was reported to have said 4,000 more US troops would be sent to the country.
US troops have been fighting in Afghanistan for nearly 16 years against a resilient Taliban.
In February General John Nicholson, commander of US forces in Afghanistan, told the Senate Armed Services Committee that leadership assesses “the current security situation in Afghanistan as a stalemate.”
He added: ”We remain concerned about multiple critical factors.”
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