Kabul (Afghanistan), oct. 26 : The death toll from crashes in southern and western Afghanistan involving two helicopters rose from four to 14 on Monday.

Reports said 14 American soldiers and civilians had died in the two incidents.

Officials described it as one of the blackest days for the United States since its 2001 invasion of Afghanistan following the 9/11 terror attack.

The tragedy came as anti-US protests erupted in Kabul over the alleged burning of a Koran.

The deadlier of the two chopper crashes took place in western Badghis province where seven soldiers and three civilians were killed.

The Nato-led force in Afghanistan said enemy fire was not believed to be the cause, while the Taliban claimed responsibility.

The Taliban also claimed to have caused a mid-air collision in the south of the country which Nato''s International Security Assistance Force (ISAF) said had killed four American soldiers.

The crash in Badghis occurred during a joint search operation by Afghan and Western forces of ''a suspected compound believed to harbour insurgents conducting activities related to narcotics trafficking'', ISAF said.

So far, 437 foreign troopers have died in Afghanistan in 2009, including 269 Americans. (ANI with inputs)