KABUL, Aug 11: Five Nato soldiers were killed by a bomb in southern Afghanistan on Thursday, as the Taliban rejected a US claim that the fighters who shot down an American helicopter had been killed in an air strike.

A United States official said that all the five slain soldiers were American citizens. The deaths came a week after the Taliban shot down a US helicopter, killing 38 people including 30 Americans, the biggest loss of US life in a single incident since the 2001 invasion.

At least 387 coalition soldiers have now been killed in Afghanistan so far this year, compared to 711 deaths in 2010, according to a tally based on the one kept by independent website icasualties.org.

South Afghanistan is the Taliban's heartland and was the focus of a US troop surge from 2010 that commanders say has made significant progress. But the militia still frequently strike troops on foot patrol or travelling in armoured vehicles with crudely-assembled improvised explosive devices (IEDs).

From April to June, 3,485 IEDs exploded or were found in Afghanistan, according to the Pentagon, a 14 per cent increase on the same period last year.

In addition, officials said five Afghan policemen were killed in an overnight clash with the Taliban in the southern province of Helmand.

“One of our police posts was attacked in Gereshk last night. Five policemen were killed,” said an official.

In the capital on Thursday, President Hamid Karzai announced that he would not seek a third term in office.

The Afghan constitution limits a president to two terms and his office issued the statement in response to “rumours” from opponents suggesting he could seek to try and change this rule. —AFP