A roadside bombing today in eastern Afghanistan killed four American troops, the US military said.

The United States and other countries are examining whether extremist groups are inciting protesters to riot around the world over cartoons of the Prophet Mohammed, a US military spokesman said today.

A US Chinook helicopter that crashed in eastern Afghanistan may have been shot down by hostile fire, and the fate of 17 American service members aboard was unclear, the US military said today. The Taliban claimed it attacked the aircraft.

Fierce battles between US and government forces and Taliban-led militants have left about 64 rebels dead, the US military said today, the bloodiest fighting in Afghanistan in nine months.