KABUL — A bomb attack killed a US service member in Afghanistan, NATO said Sunday, doubling the number of American soldiers killed in the country this year compared with 2008, according to an AFP tally.

The NATO-run International Security Assistance Force (ISAF) said the soldier died from an improvised explosive device (IED), the biggest killer of foreign troops in the eight-year battle to contain a Taliban insurgency.

"An ISAF service member from the United States died following an IED strike in southern Afghanistan Saturday," the force said in a statement.

The death takes this year's international military casualties in Afghanistan to 506, according to an AFP tally based on independent website icasualties.org which tracks military deaths in Afghanistan and Iraq.

Of those deaths, 310 have been Americans, according to the AFP tally. That figure compares with a total of 155 Americans given by icasualties for 2008.

This year has already proved the deadliest so far in the battle against the Taliban-led insurgency which followed the 2001 US-led invasion to oust the militia's extremist regime in Kabul.

The total number of foreign troops killed in Afghanistan in 2008 was 295.

An influx of extra troops this year has escalated battles in the southern provinces of Kandahar and Helmand, the Taliban heartland, as has the number of deaths of both foreign troops and the Afghan forces they are leading.

The insurgents have supplemented battlefield tactics with roadside bombs, which have taken an enormous toll.

Experts say deaths will escalate further with the arrival of reinforcements -- 30,000 from the US and 6,800 from NATO allies -- over the course of 2010.

US President Barack Obama has ordered the troop surge as part of a new war strategy that his administration hopes will be effective enough to enable the start of a troop drawdown by July 2011.

Extra troop commitments from NATO allies are expected to take to around 150,000 the total number of foreign troops operating in Afghanistan under US and NATO command in the coming year.

US Joint Chiefs of Staff chairman Admiral Mike Mullen warned during a visit to Kabul this month the violence will get worse before getting better as the Taliban dominate at least a third of the country.

"I told our troops heading here to steel themselves for more combat and more casualties," he said.

The number of foreign troops to have died in Afghanistan this year surpassed 500 with the deaths early last week of four British soldiers in the south in as many days.

The surge is pivotal to a new strategy for fighting the war against the Taliban, and is to be accompanied by a significant influx in civilians to help with development and aid.

Military officials in Kabul have said the troop influx will be gradual over the first eight months of 2010 and will be concentrated on populated areas on the ring road that connects the country.

It is also, however, expected to lead to more battles and subsequently more deaths, analysts said.

NATO officials have said that for every IED death, there can be up to eight casualties, many with horrendous injuries including loss of limbs and eyes.

The record death toll has fueled opposition among the Western public about why their troops are dying for the world's second-most corrupt country.

President Hamid Karzai won an August presidential election riddled with fraud but has pledged to clean up the endemic graft in return for the now-conditional support of the West.

Part of that effort includes training the Afghan police and army -- with Western funding and support, to take responsibility for the country's security by the end of his five-year term.

A senior Afghan military official said NATO forces killed 12 militants Sunday in an air strike in eastern Afghanistan.

The incident happened in Narang district of Kunar province, a Taliban stronghold, said General Mohammad Qasum Betanai.

"Twelve armed opposition, including their commander, were killed in a coalition forces' air strike," he said.

ISAF had no immediate confirmation of the incident.