US troops in Afghanistan have been placed on alert following the killings¹ of 16 Afghan civilians² by a US soldier.

一名美军士兵杀害了16位阿富汗平民，此举导致美国驻阿富汗部队处于戒备状态。

US officials warned of reprisals³（报复） after the soldier went on a rampage in villages near a base in Kandahar. Nine children were among those killed.

Earlier, US President Barack Obama phoned his Afghan counterpart Hamid Karzai to express condolences（慰问，哀悼） over the massacre⁴.

US Defense⁵ Secretary Leon Panetta has said a full investigation⁶ is under way.

The soldier, believed to be a staff sergeant⁷, is reported to have walked off his base at around 03:00 Sunday (22:30 GMT Saturday).

In the villages of Alkozai and Najeeban, about 500m (yds) from the base, he reportedly attacked three homes.

At one house in Najeeban, 11 people were found shot dead, and some of their bodies set alight. At least three of the child victims are reported to have been killed by a single shot to the head.

The US military said reports indicated that the soldier returned to his base after the shootings and turned himself in.

Pentagon spokesman Capt John Kirby said investigators⁸ reached the scene shortly after the attack and were interviewing the suspect.

The soldier is being detained in Kandahar and the military is treating at least five people wounded in the attacks, officials said.

The detained soldier has not been identified, although US officials quoted by AP news agency said he was from Joint⁹ Base Lewis-McChord in Washington state, married with two children, who had served three tours in Iraq and was on his first deployment¹⁰ in Afghanistan.

The killings come amid already high anti-US sentiment in Afghanistan following the burning of Korans at a Nato base in Kabul last month.

US officials have repeatedly apologised for the incident but they failed to quell¹¹（平息，镇压） a series of protests and attacks that killed at least 30 people and six US troops.