In the latest bizarre story to come out of the US "endless war" in Afghanistan, American warplanes obliterated an allied Afghan military post in an act of "self defense" on Wednesday.

The incident took place in the tribal Uruzgan province of south-central Afghanistan and reportedly began when a joint convoy of US troops and Afghan Special Forces came under fire by another unit of Afghan ground troops in what appears a major instance of accidental friendly fire resulting in a devastating two dozen total casualties on the Afghan side.

US DoD file photo: coalition jets in operation over Afghanistan.

The incident is under investigation, but US mission spokesman Bob Purtiman appeared to excuse US actions in a statement on Thursday: "We are operating in a complex environment where enemy fighters do not wear uniforms and use stolen military vehicles to attack government forces," he said.

American forces indicate they came under attack by an unknown entity. US planes flying overhead then destroyed the Afghan army post (described by the Pentagon as a "checkpoint"), which killed at least six soldiers and wounded nine others at the small base which housed a total of 17.

The US side reported no deaths or injuries, though the Pentagon would likely not release such information until a full investigation is concluded.

The US Department of Defense confirmed the incident on Wednesday, which it described as a mistaken "example of the fog of war". Pentagon Spokesperson Sgt. First Class Debra Richardson told The New York Times: “The U.S. conducted a precision self-defense airstrike on people who were firing at a partnered U.S.-Afghan force.”

Ironically US officials described the aerial bombing of the allied Afghan post as a "precision airstrike," per the AP:

The soldiers were killed by friendly fire Wednesday in what was supposed to be a precision airstrike by U.S. forces supporting Afghan soldiers battling insurgents near the city of Tarin Kot in Uruzgan province.

It was the second major incident to cause Afghan casualties following a prior fight with Taliban: "For the second time in a few days, an Afghan Army base was destroyed on Wednesday — but this time by American airstrikes that followed a firefight between the Afghans and Americans, Afghan officials said," the NYT report noted.

Last year the Pentagon acknowledged that war in Afghanistan is costing American taxpayers $45 billion per year, with a number of public studies putting the total figure at over $1 trillion since the US war began nearly two decades go.

The "endless war" has become more expensive, in current dollars, than the Marshall Plan, which was the reconstruction effort to rebuild Europe after World War II.