Nine coalition troops were killed on Tuesday when a helicopter crashed in Afghanistan's south, the NATO-led force said, making 2010 the deadliest year of the nine-year war.
Two NATO service members, an Afghan soldier and a U.S. civilian were wounded in the crash. They were taken to hospital for treatment, the International Security Assistance Force (ISAF) said in a statement.
There was no indication of the nationality of the dead troops, ISAF said in a statement. An ISAF spokesman said more information would be released later.
There was no enemy fire in the area when the aircraft crashed and the cause is under investigation, ISAF said.
The deaths take the toll so far in 2010 to at least 529, according to monitoring website iCasualties.org. Last year, the previous deadliest, 521 foreign troops were killed.
Violence in recent months has soared to its highest levels since the removal of the Taliban by U.S.-backed Afghan forces in late 2001.
There are almost 150,000 foreign troops fighting a growing Taliban-led insurgency in Afghanistan, supporting about 300,000 Afghan security forces. U.S. President Barack Obama ordered in an extra 30,000 troops, the last units of which arrived this month.
Aircraft crashes are not infrequent in Afghanistan. In October 2009, two helicopter crashes killed 11 U.S. soldiers and three U.S. civilians.