Washington: NATO and Afghan forces came under fire from across the Pakistan border before they called in a deadly airstrike on two Pakistani military posts that left 24 soldiers dead, media reports quoted Afghan and western officials as saying.

As Pakistan simmered over the killings, Wall Street Journal quoted US officials in Kabul as saying that insurgents may have been firing into Afghanistan near the Pakistani border which prompted coalition forces to strike back.

The account challenges Islamabad's claims that the attacks, which have plunged US-Pakistan ties to new lows, were unprovoked and risked stoking fresh tensions as the incident has left US-Pakistan relations in tatters.

Afghan officials working in the border area where the attack took place said that the joint forces was targeting Taliban militants in the area when it received fire from the Pakistani military outpost.

That prompted the coalition forces to call for an air attack on the Pakistani forces, the Afghan officials said and also claimed that Pakistani officials were informed of the operation before it took place.

"There was firing coming from the position against Afghan army soldiers who requested support and this is what happened," WSJ quoted an Afghan official as saying as the top US commander Gen. John Allen held a meeting in Kabul to discuss the incident.

The Afghan officials said the government believes that he fire came from the Pakistani base and not from insurgents operating nearby. A view bolstered by a western official who also said that coalition forces were fired on from a Pakistani army base.