The chief U.S. watchdog in Afghanistan says he is deeply concerned about the ability of the Afghan military to take over security responsibility when U.S. troops withdraw next year and warned the country could once again become a safe haven for terrorists.

A teenage Afghan boy fatally stabbed a U.S. soldier who was playing with local children, military spokespeople said Monday.

An unspecified number of American and Afghan troops were killed by an Afghani in uniform who opened fire on Monday in the eastern province of Wardak.

Afghan security personnel attacks against U.S. and NATO troops rose sharply last year despite a NATO command overhaul of how local army and police recruits are screened.

A senior-level Pakistani Taliban commander has been captured in the southeastern region of Afghanistan — a sure sign of warming relations between the two countries, military analysts say.

Afghan police on Sunday arrested six men and seized suicide vests, assault rifles and more than 50 hand grenades during a raid on a residential building in central Kabul, senior officials said.

A vehicle driven by a suicide bomber exploded at the gate of a major U.S. military base in eastern Afghanistan on Wednesday, killing the attacker and three Afghans, Afghan police said. The Taliban claimed responsibility for the attack.

The policewoman who killed an American contractor in Kabul is a native Iranian who came to Afghanistan and displayed "unstable behavior" but no known links to militants, an Interior Ministry spokesman said.

An Afghan policewoman walked into a high-security compound in Kabul Monday and killed an American contractor with a single bullet to the chest, the first such shooting by a woman in a spate of insider attacks by Afghans against their foreign allies.