Updated

The Afghan border policeman who killed six American service members during a training mission had been on the force for three years and had no criminal background, the Interior Ministry said Tuesday.

The gunman, who was killed in Monday's shootout, opened fire as the group was on its way to shooting practice in Nangarhar province near the Pakistan border, Interior Minister Bismullah Mohammadi told reporters.

He also has a brother on the force, the minister said.

The Taliban has claimed responsibility for the attack, saying the officer had enlisted as a sleeper agent in order to have an opportunity to kill foreigners.

The bloodshed — which appeared to be the deadliest attack of its kind in at least two years — underscored one of the risks in a U.S.-led program to train enough recruits to turn over the lead for security to Afghan forces by 2014.

Attacks on NATO troops by Afghan policemen or soldiers, although still rare, have increased as the coalition has accelerated the program. Other problems with the rapidly growing security forces include drug use, widespread illiteracy and high rates of attrition.

Also Tuesday, the Interior Ministry said Afghan gunmen attacked a construction company in Kabul province, wounding one security guard and kidnapping nine others in the mountainous Sarobi district, about 27 miles (45 kilometers) east of the capital, Kabul.

Nine other guards escaped the attack, which happened Monday, said Zemeri Bashary, an Interior Ministry spokesman. The gunmen also seized several rifles.

In other violence, an insurgent attack in eastern Afghanistan killed a NATO service member on Tuesday, the military coalition said. The victim was not immediately identified.

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AP writers Elizabeth A. Kennedy and Heidi Vogt contributed to this report from Kabul.