Images from the attack on Monday, verified by a U.S. military officer familiar with the incident, show the burning U.S.-supplied Black Hawk along with a bundle of guiding wire, a distinct feature on some types of anti-tank guided missiles.
For the duration of the war, U.S. military intelligence officers have repeatedly made claims of weapons and supplies flowing from Pakistan, Iran, Russia and other Central Asian countries to the Taliban, but often with little proof. American officials have closely tracked the appearance of surface-to-air missiles and other threats to aircraft, as any type of foreign involvement with such types of weapons would be contentious and substantially increase the risk to American and Afghan forces.
Since anti-tank guided missiles are not designed to specifically target aircraft, their introduction to the conflict is less likely to draw significant condemnation from the Americans, the U.S. military officer said, though it would certainly be an escalation. The United States provided such weapons to Syrian opposition fighters in 2014 and portable surface-to-air missiles to Islamist fighters in the 1980s.
About 60,000 Afghan security forces have been killed since 2014, when U.S. forces began drawing down. And since the beginning of the year, despite a peace agreement between the United States and the Taliban in February, Afghan troops and civilians continue to suffer heavy losses.
Speaking at an event in Kabul on Tuesday, Mr. Ghani said 3,560 Afghan forces had been killed and nearly 6,800 others wounded since the deal between the United States and the Taliban. The casualties are possibly higher, some Afghan officials suggested, with many doubting that the number included the losses of pro-government militias who bear the brunt of the fighting. And from Jan. 1 to June 30, 1,282 civilians were killed and 2,176 were wounded, according to a United Nations report released on Monday.
On Tuesday, after weeks of deadly attacks on Afghan forces, the Taliban announced a three-day cease-fire for the Muslim festival of Eid al-Adha. The announcement came soon after Mr. Ghani said a prisoner swap that had faced opposition from his government would be completed and that direct negotiations with the Taliban would start in a week.
But the violence continued right up to the time of the cease-fire, with a car bomb detonating at a crowded roundabout in Pul e Alam, a city about 40 miles south of Kabul. Officials said the target was a security convoy, but the 15 people killed and 30 wounded were a mix of civilians and military.