NATO says its troops opened fire on a bus in southern Afghanistan Monday, killing at least four people and wounding 18 others.
NATO says its patrol fired on a large vehicle after the driver refused warnings to stop in the Zhari district of Kandahar province. Upon inspection, NATO says its forces discovered the vehicle was a passenger bus.
A woman was among those killed. NATO soldiers took some of the wounded to a military hospital.
In a statement, the alliance says it deeply regrets the tragic loss of life. A combined NATO and Afghan team arrived in Zhari to investigate the incident.
Dozens of Afghans took to the streets in Kandahar city to protest the killings. Demonstrators chanted "Death to America" and called for the downfall of Afghan President Hamid Karzai. They also blocked the main road out of the city.
President Karzai condemned the killings.
The Afghan leader issued a statement, saying the shooting of a civilian bus violates NATO's commitment to safeguard civilian life.
U.S. General Stanley McChrystal, the commander of U.S. and NATO forces in Afghanistan, told Afghan leaders earlier this month that troops under his command are making the strongest efforts possible to avoid civilian casualties, but he acknowledged his forces sometimes make mistakes.
Elsewhere in Kandahar Monday, Afghan officials say three suicide bombers attacked the Afghan intelligence services compound resulting in a deadly gunfight.
Afghan officials say one bomber blew himself up and another was killed by security forces. At least nine people were wounded in the attack.
And the Taliban is demanding the release of prisoners in exchange for two French journalists kidnapped December 30 from eastern Afghanistan. The Taliban made the demand in a video posted late Sunday.
Some information for this report was provided by AP, AFP and Reuters.