Another U.S. soldier has been killed in Afghanistan as violent protests continue for the sixth day over the burning of the Koran by American forces.

During fresh protests in the northern Afghan city of Kunduz, one U.S. soldier and one local civilian were killed by hand grenades thrown by protesters.

A police officer in Kunduz says 20-thousand demonstrators poured onto the streets and tried to enter the coalition forces base, and some armed members threw grenades inside the base which caused the casualties.

The officer says six other U.S. service members and 15 Afghan police officers including a police chief were also injured.

At least 32 people, including five U.S. soldiers, have died since the protests erupted last Tuesday all across Afghanistan after U.S. personnel put the Korans into a rubbish incinerator at Bagram air base near Kabul.

American officials have called the incident a mistake and issued a series of apologies.