Kabul - US-led coalition forces mistakenly bombed an Afghan national army position in eastern Afghanistan early Wednesday, killing nine soldiers and wounding three others, officials said.

The incident took place in Sayedkhail district of the south-eastern province of Khost when a coalition convoy was returning from an operation, the US military said in a statement.

"Initial reports from troops on the ground indicate that this may be a case of mistaken identity on both sides," the statement said.

"At 2 am today during a bombardment of international forces, nine Afghan army soldiers were killed and three were wounded," the Afghan defence ministry said in a statement, adding that one of the wounded soldiers was in critical condition.

Coalition forces were coordinating with the Afghan government for a joint investigation into the incident, the US military statement said.

The friendly-fire incident could strain relations between the coalition troops and Afghan army forces, who are fighting the Taliban-led insurgency in the country. Around 70,000 international troops are stationed in Afghanistan. (dpa)