Three American soldiers have been killed in an attack in Afghanistan's eastern border region, US and NATO officials have said.

A US official said on Sunday that fighters in Paktia province killed the soldiers from the NATO-led International Security Assistance Force (ISAF).

"Three International Security Assistance Force service members died following an enemies of Afghanistan attack in eastern Afghanistan today," the ISAF said in a statement.

In line with ISAF policy, the nationalities of the soldiers were not given and casualty identification was left to the relevant nation.

Howver, US sources have said the soldiers were American.

The deaths bring the number of fatalities among foreign troops this year to 114, according to the independent icasualties.org website, which recorded 402 such deaths in 2012.

The last NATO soldier to be killed in action in Afghanistan was late last month.

Paktia is one of several provinces that border Pakistan and have endured some of the highest levels of fighting during the US-led 12-year war in Afghanistan.

US soldiers based in Paktia are now rarely involved in combat operations.

The US handed over security responsibility to Afghan security forces this year.

US soldiers now primarily train their Afghan colleagues.

The NATO-led mission has about 100,000 international troops in Afghanistan, of which about 68,000 are American.

Those numbers are expected to reduce sharply before the official end of the NATO-led combat mission, on December 31, 2014.