The US-led International Security Assistance Force (ISAF) took nearly a full day to confirm that an explosion on the aircraft was caused by an insurgent attack, which the Taliban militia had been quick to claim.
An AFP correspondent in Kunar province said he saw three helicopters flying over the Ghash area of Marawar district and then heard the sound of rocket fire, after which two helicopters flew off and a gun battle broke out.
"Eight people were wounded and one killed after a rocket-propelled-grenade was fired at an International Security Assistance Force helicopter in Kunar province today," the military said.
There were 26 people on board the helicopter, which ISAF identified as a US CH-47 Chinook.
The helicopter had just landed at a military outpost and was off-loading through the rear ramp when the RPG was fired into the cargo bay.
"The explosion resulted in one Afghan interpreter killed, seven ISAF service members and one Afghan border police member wounded," the military said.
Eastern Afghanistan is one of the most volatile parts of the country, where Taliban and other Islamist insurgents have carved out strongholds. It lies just across the border from Pakistan, where militant groups have rear bases.
The interior ministry said separately that six civilians, including a woman and two children, were killed Tuesday when insurgents fired a rocket into the Ghibi Khil area of southeastern province Paktika.
The war is now in its deadliest year. Around 152,000 foreign troops under US and NATO command are fighting a Taliban insurgency that has steadily expanded since the 2001 US-led invasion brought down their regime.
NATO and US troops rely heavily on helicopters for transporting troops and supplies across the country, where convoys travelling on largely poor roads are vulnerable to attacks by insurgents.
While helicopter accidents are not uncommon, the Taliban have attacked NATO air assets in the past and militia spokesman Zabihullah Mujahid claimed that the insurgent group had shot down the helicopter on Tuesday.
A NATO soldier died on Tuesday in a bomb attack in southern Afghanistan, the military said, but as a matter of policy ISAF no longer discloses the nationalities of troops killed in combat.
The death took to 576 the number of foreign troops killed in 2010, according to an AFP toll based on the independent website icasualties.org.
The conflict has killed more than 2,140 international soldiers since the 2001 invasion replaced the Taliban with a Western-backed administration.
On Tuesday, the International Committee of the Red Cross (ICRC) said the number of wounded being treated at the main hospital in Kandahar, in the heart of the conflict-torn south, has soared to a record high.
Thousands of NATO and Afghan troops are fighting to control Kandahar city in Operation Dragon Strike.
As the Taliban's spiritual capital and the largest city in the south, the fate of Kandahar is considered crucial to a US-led campaign to beat back the Taliban as quickly as possible and restore confidence in the Afghan government.
About 1,000 patients with weapon-related injuries were registered at the Mirwais Regional Hospital in August and September 2010, almost twice as many as the same period last year, the ICRC said.
"Our greatest challenge consists in maintaining access to the areas hardest hit by the fighting, but the increase in the number of armed groups is making this much harder for us," said Reto Stocker, the ICRC head in Kabul.
Western public opinion is growing increasingly tired of the war, angry over corruption within President Hamid Karzai's government and mounting casualties as the conflict pushes into its 10th year.
In Italy, Foreign Minister Franco Frattini said Rome would start withdrawing its troops next year, making the comments in an interview published on the same day as a funeral for four Italian soldiers killed in the war.
Italy is the fifth largest contributor of foreign troops in Afghanistan, deploying around 3,400 troops on the ground.
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