KABUL, April 15: Afghan and NATO forces killed at least 10 Taliban in an overnight assault in eastern Afghanistan, hours before a suicide bomber killed four people on Sunday in rising violence after the annual winter lull.

The attacks came as Kabul again ruled out any hostage swap to free two French aid workers held by the rebels, who have threatened to behead them and send their heads to Paris.

In addition to killing 10 insurgents, the NATO and Afghan troops wounded 15 Taliban and arrested two in the overnight pre-emptive strike in Paktika to head off a rebel attack, provincial Governor Mohammad Akram Khpalwak told Reuters.

To the south, in the Taliban heartland of Kandahar province, a suicide bomber on a motorcycle killed four Afghans working for a US security firm, police said. Earlier a provincial official had said the attack killed two policemen.

On Saturday, US-led coalition forces also said they and Afghan troops had killed 35 Taliban in a fierce five-hour battle late last week in Helmand, the main opium-producing centre.

The Taliban have vowed to step up suicide bombings as fighting against US-led forces intensifies after winter.

The Taliban have also kidnapped three foreigners and several Afghans this year to try to press the government to release comrades from jail and to begin peace talks.

On Saturday, the insurgents released a brief black-and-white video of the two French aid workers -- a woman who calls herself only Celine and a man who calls himself Eric -- pleading for help from the French government.

VIDEO: In the tearful video, filmed on Friday, they said in English they would be beheaded and their heads sent home to France if Paris ignored the Taliban's demands.—Reuters