KABUL, Afghanistan — Taliban insurgents dealt a serious blow to one of the Afghan Army’s most highly regarded units on Friday, killing 13 soldiers and overrunning their remote outpost in eastern Afghanistan.
According to Afghan security officials, speaking on the condition of anonymity because of the nature of the Taliban victory, the 13 soldiers constituted the entire complement at the checkpost. One police official said that a force of 200 Taliban fighters had opened fire with heavy weapons and finally set the post on fire; most of the deaths were from the flames.
It was one of the bloody insurgent attacks in the current spring offensive that have helped drive the rate of government fatalities to the highest level of the war. Afghan soldiers and police officers are dying at more than double the rate of a year ago, according to military officials.
The numbers both underscore how much more of the fighting has been handed over to Afghan forces and raise questions about how ready those forces are for the increased responsibility, even as the insurgents ratchet up their much-anticipated spring onslaught.
There have been a number of high-profile insurgent attacks on the ground this year, not just the remote-control and suicide bombings the Taliban favored in the past. The shift suggests that they are testing how well Afghan forces can operate on their own at a critical juncture in the planned withdrawal of the American military.
The NATO transfer to Afghan control is scheduled to finish in the next few months, with Afghan forces taking over security in 100 percent of the country, and NATO and American military forces moving to a support and training role as their numbers diminish.
“We know the enemy’s going to come out hard this summer, so the numbers are going to go up,” said Col. Thomas Collins, a spokesman for the International Security Assistance Force.
Friday’s attack was on the Third Battalion of the Second Brigade, one of only a handful of Afghan Army battalions rated by the United States military as independent and able to operate on its own without foreign advisers. It was one of two such battalions that had been deployed without advisers recently in Kunar Province, according to a military official, who spoke on the condition of anonymity because he was not authorized to discuss the subject.
The Third Battalion was assigned to hold the Narai district, a rugged, mountainous area near the Pakistani border, on a route used by insurgents.
A spokesman for the Taliban, Zabiullah Mujahid, took credit for the attack and claimed that 15 soldiers had been killed and that the insurgents had captured all of their weapons and ammunition.
It was a measure of the delicacy of the episode that officials publicly played down the death count, with a spokesman for the 201st Corps confirming only that an attack had taken place and the Kunar Province police chief, Gen. Habib Saidkhelli, claiming that only two soldiers had been killed.
The Narai district police chief, Mohammad Yousuf, confirmed that 13 soldiers had been killed.
The Third Battalion has been widely praised as among the best of the Afghan Army’s formations.
The soldiers at the checkpost were taken by surprise because the Afghan and American militaries were concentrating on a joint operation elsewhere in Kunar, said a military official in the area.
The Second Brigade commander, Col. Hayatullah Aqtash, flew up in his personal helicopter with supplies on Friday morning to begin rebuilding the outpost, the official said.
Colonel Aqtash, reached by telephone, was dismissive of the attack. “It is a routine incident,” he said. “Every day we face such attacks.”
While it is still early in the spring fighting season to generalize, the insurgents have attacked several times recently using foot soldiers or made what the military calls “complex attacks,” involving bombings as well as firefights. Last year, the insurgents relied largely on suicide bombers and roadside bombings and avoided engaging directly with Afghan or international military forces.
In March, ground attacks by the insurgents killed four police officers and four Afghan soldiers in the Dangaam district of Kunar Province. Officials there said Friday’s attack was the deadliest in at least six months.
In northern Badakhshan Province, an area with little previous insurgent activity, Taliban forces ambushed a convoy and killed 17 Afghan soldiers sent to reinforce police posts on March 7. Most were killed after being captured, according to Afghan officials.
Then on March 25, 10 more Afghan soldiers were captured in the same area; they are still being held.
On April 3, one of the deadliest insurgent attacks of the war was set off in western Farah Province by nine Taliban fighters dressed as Afghan soldiers. They stormed a government compound, killing 10 soldiers and 34 civilians, and wounding more than 100 people.
Colonel Collins said that the increased death toll among Afghan forces was “tragic,” but that it had not so far had any long-term impact. “It doesn’t seem to be impairing their recruiting any,” he said.
The Afghan National Army has to replace and train nearly a third of its force every year because of desertions and attrition.
The death toll among Afghan forces has been steadily climbing in recent years as their numbers have grown and they have taken over more of the fighting. The army lost more than 1,000 soldiers in 2012, and the police lost 1,800 officers, according to Afghan government estimates. The army has 146,000 soldiers, with police and other units bringing total security forces to 352,000 last year.
Late last year, Gen. Mohammad Zahir Azimi, the spokesman for the Afghan military, said at a news conference at NATO headquarters that 110 soldiers and 200 policemen were dying each month.
Asked about those numbers on Friday, however, he repudiated them, but said he did not have correct figures immediately available.
Nonetheless, NATO officials have said those numbers are generally accurate.
By comparison, 25 NATO soldiers, most of them Americans, were killed in the first three months of 2013, according to figures compiled by icasualties.org, an independent monitoring group. A third of them died in aircraft accidents, not hostile attacks.