Afghan National Army soldiers keep watch as Afghans gather outside a U.S. base in Panjwai district Kandahar province, March 11, 2012. Coalition forces killed 15 civilians in a shooting spree in Afghanistan's southern Kandahar province on Sunday, the defence ministry said, in an incident likely to deepen the growing divide between Washington and Kabul.

Kandahar residents are bracing for trouble in the streets after a U.S. soldier went on a shooting rampage and killed 16 people in villages southwest of the Afghan city.

Funerals for the dead are expected on Monday, and the ceremonies could become another flashpoint for local anger against international forces. Riots swept across the country after U.S. forces mistakenly burned copies of the Koran last month; the unrest killed at least 29 Afghans and six American soldiers.

“It’s calm in the city, but people are sad and shocked,” Ehsanullah Ehsan, a school director in Kandahar, said by telephone.

Mr. Ehsan runs the Afghan-Canadian Community Centre, one of many projects that received Canadian funding in recent years as the international forces struggled to build goodwill in the Taliban heartland.

“This might incite certain uprisings or things like that, but we still don't know what will happen,” the director said. “Will they just bury their dead or start demonstrations and protests? We don't know yet.”

Thunderclouds were rumbling over the city, Mr. Ehsan said, which could be a good sign.

“Hopefully if it rains nobody will come out in the streets,” he said.

Witnesses told several media outlets that a U.S. soldier left a military outpost in the early hours of Sunday morning and rampaged through a series of mud-walled homes nearby. Villagers later collected some of the dead, including women and children, and displayed their bodies in a protest near the base.

The incident will also revive bitter memories in Kandahar of the four U.S. soldiers who were convicted in 2010 of killing civilians and collecting their body parts for trophies.

U.S. General John Allen, commander of NATO troops in Afghanistan, quickly apologized for the “deeply appalling incident” and promised an investigation.

“We will maintain custody of the U.S. service member alleged to have perpetrated this attack,” Gen. Allen said in a statement. “And we will co-operate fully with local Afghan authorities as we ascertain all the facts.”