Nine people were killed when shooting broke out during a mass demonstration in a provincial Afghan town over the alleged burning of a Koran by foreign troops, police said on Wednesday.
The violence erupted on Tuesday in the Garmsir district of the southern province of Helmand over rumours that NATO-led forces had defiled a copy of the Muslim holy book during a military operation, local residents and police said.
NATO said it had no information confirming the civilian deaths, but that it was investigating the incident along with Afghan security officials.
"Eight protesters were killed when the protesters attacked national security officials in Garmsir," deputy provincial police chief Kamaluddin Khan told AFP.
The shooting of the protesters occurred after an Afghan guard outside a nearby building was killed by gunfire "from the demonstrators' side," he said.
Khan said 13 civilians and two Afghan policemen were also wounded in the incident.
NATO's International Security Assistance Force (ISAF) said in a statement on Tuesday that its troops had shot dead an "insurgent sniper" who had shot an Afghan official in the Garmsir area.
But a spokesman for the force said there was no information to back up claims of civilian deaths in the incident, adding that investigations with Afghan security officials were under way.
"We are continuing with our investigation of the reports that have appeared in media," Sergeant Jeff Loftin said on Wednesday.
"The only shot we know that was fired was from a compound rooftop. The gunman was positively identified as a sniper and we took him out.
"Other than that we don't know of any other shooting or where these figures come from," he said.
ISAF said in a statement on Tuesday that during the protest, "an insurgent sniper shot an Afghan official who was within FOB (Forward Operating Base) Delhi in Garmsir district".
"ISAF service members identified the insurgent sniper, shot and killed him. There were no other injuries or shots fired," it added.
The incident occurred when more than 1,000 Afghan villagers gathered in Garmsir to protest over the alleged burning of a Koran during a NATO operation on Monday, local residents and police said.
A doctor at the emergency hospital in the provincial capital Lashkar Gah, who spoke on condition of anonymity, said that more than 10 people had been brought in "with gunshot wounds to the stomach, head and legs".
"Two of them are in serious condition," he said.
Helmand provincial governor Daud Ahmadi has sent a delegation of police and government officials to Garmsir to investigate the incident, a spokesman for his office said.
"The investigation has began and the delegation is expected to come back with a report to the governor by this evening," the spokesman said.