The Taliban promised revenge Monday for the alleged massacre of 16 Afghan civilians by an American soldier, an incident which may pose the biggest threat yet to the shaky U.S. alliance with Afghanistan’s government.

U.S. forces have boosted security in Kandahar province, where the shootings happened on Sunday. There is a fear of reprisal attacks against Westerners, but no widespread protests were reportedly early Monday morning.

The Taliban vowed revenge in a statement against what they called “sick-minded American savages” following the killings.

Afghan President Hamid Karzai is demanding an explanation from U.S. forces into how this attack could have happened, and has called the incident, “an assassination,” saying the killing of civilians cannot be forgiven.

Continue Reading on www.cbsnews.com