In a several-hour battle, 13 Afghan soldiers and policemen were killed and 11 others were wounded, said Abdul Ghani Sabri, the deputy provincial governor. Seven Taliban fighters were also killed, Sabri said.
Sixteen other Afghan troops were captured by the militants, who also took most of the 47 vehicles being transported in the convoy, Khan said.
Following the clash, helicopters were dispatched to the area and fired at the militants, Khan said.
Insurgent attacks in Afghanistan are up 40 percent from 2007, military officials say. A tally of official figures provided to The Associated Press show that more than 5,400 people have died in insurgency-related violence this year. Most of the casualties are suspected militants.
The U.N. warned Thursday that the Taliban could receive $500 million dollars from Afghanistan's opium trade this year - money that will help finance insurgent attacks.
The potential profits are dramatically higher than the $100 million the Taliban is believed to have received last year from the multibillion-dollar trade.
In eastern Afghanistan, meanwhile, NATO-led troops fired more than 20 artillery rounds inside Pakistan, from where insurgents were attacking their bases in Paktika province on Thursday, the military alliance said.
The artillery attacks killed several insurgents and caused several secondary explosions, indicating the presence of ammunition at the locations, it said in a statement.
There have been a number of artillery attacks by NATO-led troops inside Pakistan's tribal region, which the military alliance says were launched in coordination with Pakistan's authorities.
Thursday's strikes came at a time when NATO and Pakistani forces have been cooperating in so-called Operation Lion Heart - a series of complementary operations that involve the Pakistani military and Frontier Corps and NATO on the Afghan side, U.S. military officials say.
Militants use Pakistan's lawless tribal areas as safe havens from which to launch attacks on U.S. and Afghan troops in Afghanistan and also within Pakistan.
Separately from NATO operations, U.S. forces have launched several airstrikes on militants in Pakistan's tribal areas since August, deepening already widespread antipathy among Pakistanis toward the presence of Western forces in the region.
Afghan President Hamid Karzai has also expressed frustration with the tactics of foreign forces in his country, saying civilian casualties at the hands of NATO and American troops have undermined support for his government.
There have been several incidents in which Western troops have fired on civilian vehicles, fearing they were suicide attackers trying to ram their convoys.
On Friday, Kabul Police Chief Ayub Salangi reported one such incident, saying a convoy of foreign troops shot at a civilian vehicle. NATO denied the account.
The alliance said its troops went to the area after a foreign contractor was involved in a car accident.
"On their arrival, the patrol found a large crowd surrounding the contractors' vehicles," a NATO statement said. "It can be confirmed that no personnel in this patrol discharged their weapon during the incident."
Two civilians were killed and two wounded, said Mohammad Zia Mohammad, a police official. One of the dead was a 5-year-old child, he said.
