The US soldier who was accused of killing 16 civilians in Afghanistan has been transferred out of the country, the Pentagon said Wednesday.

"He has been flown outside of the country, based on legal recommendation," said Pentagon spokesperson John Kirby without disclosing where the soldier had been transferred.

Kirby explained that the reason the soldier has been moved out of Afghanistan was because there are no "appropriate detention facilities" in the country, adding that the move did not necessarily mean that the trial would be held outside Afghanistan. The suspect has not been charged, pending investigation.

US commander in Afghanistan John Allen made the transfer decision, reported Xinhua.

The suspect, an Army staff sergeant who the Pentagon said had acted alone, left his base in Panjwai district of Kandahar province Sunday morning and killed 16 Afghan civilians, including women and children.

The incident occurred amid rising tensions after the burning of the Quran and other religious materials at the US-run Bagram Airbase near Kabul sparked nationwide protests in Afghanistan.

US President Barack Obama and Defense Secretary Leo Panetta, in their telephone calls to Afghan President Hamid Karzai Sunday, have promised full investigation into the incident and bring anyone responsible to justice.