(Updates bomb toll, details)

By Terry Friel

KABUL, April 15 (Reuters) - 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 U.S. security firm, police said. Earlier a provincial official had said the attack killed two policemen.

On Saturday, U.S.-led coalition forces also said they and Afghan troops had killed 35 Taliban in a fierce 5-hour battle late last week in Helmand, the main opium producing centre.

The Taliban have vowed to step up suicide bombings as fighting against U.S.-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.

EMOTIONAL TAPE

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.

But the Taliban have issued no public ransom demand for their release. Italian Daniele Mastrogiacomo, who was kidnapped in Helmand last month, was freed after two weeks when Kabul released five senior Taliban prisoners.

His Afghan driver and translator were beheaded.

Afghan Foreign Minister Rangeen Dadfar Spanta on Sunday repeated President Hamid Karzai's pledge there would be no more hostage swaps.

"We will avoid the exchange of hostages with the criminals," Spanta told reporters. "If we do it once or twice, it will become a procedure. It won't have an end."

The Mastrogiacomo deal drew criticism in Afghanistan and Italy for encouraging the Taliban to take more hostages. They are also holding five Afghan health workers and have threatened to kill one soon unless the government starts peace talks.

Karzai's palace said on Saturday French President Jacques Chirac had phoned the Afghan leader to ask for help.

"President Hamid Karzai assured President Chirac that the relevant Afghan institutions will spare no effort in securing the release of the kidnapped French nationals and their Afghan colleagues," the palace said in a statement.

Last year was the bloodiest since the Taliban were ousted in 2001 and many expect this year to be even more violent.

Several hundred civilians, scores of Taliban, dozens of Afghan forces, some aid workers and more than 30 foreign troops have died so far this year.

AlertNet news is provided by