KABUL, Afghanistan — Like hundreds of thousands of Afghan men, he volunteered in the national army, ran drills in the mud, carried an automatic rifle, and worked alongside coalition mentors struggling against a hard-core insurgency.
But he was not one of them.
On Saturday, he walked into a meeting of NATO trainers and Afghan troops at Forward Operating Base Gamberi in the eastern province of Laghman and detonated a vest of explosives hidden under his uniform.
Five NATO troops, four Afghan soldiers and an interpreter were killed in the deadliest sleeper agent assault. Four Afghan soldiers and three interpreters were wounded.
The Taliban claimed responsibility for the bombing and said the soldier was a sleeper agent who joined the army a month ago, a contention confirmed by an Afghan army official.
"Today, when there was a meeting going on between Afghan and foreign soldiers, he used the opportunity to carry out the attack," Taliban spokesman Zabiullah Mujahid said in an e-mail to reporters.
Attacks by insurgents donning security uniforms are a relatively rare but recurrent problem as NATO and Afghan forces work more closely together. Afghanistan's security forces are also ramping up recruitment of Afghan soldiers and police officers so they can take the lead in securing their nation by the end of 2014, adding more than 70,000 police and soldiers last year in an effort to reach 305,000 troopers by the end of this year.
Afghan security forces are supposed to be vetted by past employers or even village elders, but in a country where unemployment is about 35 percent, the literacy rate is about 28 percent, and computerized record-keeping is a novelty, background checks are often rudimentary.
The explosion took place at 7:30 a.m., as many people on the base were beginning the morning shift and as NATO and Afghan service members conducted a meeting, according to a NATO spokesman.
After the explosion, Black Hawk helicopters swooped down to carry the dead and wounded to hospitals.
Baz Mohammad Sherzad, the director for health in nearby Nangarhar province, said the bodies of four Afghan soldiers brought to a hospital in Jalalabad were too badly damaged to determine their military rank.
NATO declined to provide further identifying information about its soldiers killed in the blast, pending notification of their next of kin.
On Friday, a suicide bomber dressed as a police officer blew himself up inside the Kandahar police headquarters complex, killing the top law enforcement officer in the restive southern province, Khan Mohammad Mujahid.