The US is carrying out air strikes in Afghanistan to support government forces fighting against Taliban insurgents, who have made rapid gains amid the withdrawal of US and other foreign troops.
US military aircraft conducted several air strikes "in defence of our Afghan partners in recent days", Maj Nicole Ferrara, a US Central Command spokeswoman, told Bloomberg on Saturday.
Maj Ferrara did not specify the type of aircraft used but the Daily Mail reported earlier on Saturday that President Joe Biden ordered B-52 bombers and AC-130 Spectre gunships to strike enemy fighters advancing towards cities such as Kandahar.
The Taliban overran two provincial capitals on Friday and Saturday, the group's most significant gains since stepping up attacks across the country as foreign forces began to leave in May.
Afghanistan control map
The Taliban last week threatened to attack officials in Kabul if the government did not stop raids on fighters by the Afghan Air Force.
The group claimed a bomb and gun attack on the Defence Minister's home on Tuesday night and the assassination of the government's top media official on Friday.
On Saturday, an Afghan Air Force pilot was killed in a blast in Kabul.
The pilot, Hamidullah Azimi, died when a sticky bomb attached to his vehicle detonated, officials said.
Five civilians were wounded in the explosion.
Taliban spokesman Zabihullah Muhajid said the group carried out the attack.
Azimi was trained to fly US-made UH-60 Black Hawk helicopters and served in the Afghan Air Force for almost four years, the force's commander, Abdul Fatah Eshaqzai, told Reuters.
He had moved to Kabul with his family a year ago owing to security threats, Mr Eshaqzai said.
Officials say at least seven Afghan pilots were previously killed in a Taliban assassination campaign.
US and Afghan officials believe it is a deliberate effort to destroy Afghanistan's corps of military pilots, trained by the US and Nato, as fighting escalates across the country.
The Taliban have no air force but want to level the playing field by continuing major ground offensives that have allowed the group to seize territory since May.
Emboldened by Washington's announcement that it was ending its military mission by the end of August, the Taliban launched a military blitz across the country that has gained momentum in recent days.
On Friday, the insurgents captured their first provincial capital in years when they took control of Zaranj, on the border with Iran in Afghanistan's southern Nimruz province. On Saturday, the Taliban took control of Sheberghan in Jawzjan province.
As the Taliban set its sights other cities, the Afghan Air Force played a crucial role in holding them back.
Azimi's death came days after the Special Inspector General for Afghanistan Reconstruction (Sigar), in a report to the US Congress, said the attacks on pilots by the Taliban were another "worrisome development" for the Afghan Air Force as it reeled from the surge in fighting.
In its quarterly report covering the three-month period to the end of June, Sigar described the air force as increasingly under strain and becoming less capable of fighting.
Its fleet of UH-60 Black Hawk helicopters had a 39 per cent readiness rate in June, about half the level of April and May.
"All aircraft platforms are overtaxed due to increased requests for close air support, intelligence, surveillance, reconnaissance missions and aerial resupply now that the [Afghan military] largely lacks US air support," the report said.