Bomb hits U.N. convoy, kills driver, 4 guards

~ Attack comes a day after a report accused Taliban militants of committing war crimes targeting civilians.

KABUL, Afghanistan -- A powerful remote-controlled bomb destroyed a U.N. vehicle in southern Afghanistan's main city Tuesday, killing four Nepalese guards and an Afghan driver, officials said.

The attack on a three-vehicle U.N. convoy in Kandahar was the bloodiest in Afghanistan for the world body since the hard-line militia's 2001 ouster and illustrated how violence continues to impede much-needed reconstruction.

The convoy was driving along the side of a canal in Kandahar when unidentified assailants detonated the charge. It struck a gray sport utility vehicle, killing the four guards and their driver, police and the U.N. said.

An Associated Press reporter saw two charred bodies lying on the road near the damaged vehicle. The explosion blew off two of the car's doors and gouged a crater in the road.

"Intentional attacks on civilians are a clear violation of international humanitarian law and the U.N. will be pursuing full accountability for those who are behind this," a U.N. statement said.

While there was no immediate claim of responsibility, the attack came a day after a Human Rights Watch report accused Taliban militants of committing war crimes by targeting civilians.

The rights group said nearly 700 Afghan civilians were killed by militants in 2006 -- more than three times the civilian deaths attributed to U.S. and NATO forces, which have been criticized for using excessive force in civilian areas.

Violence in the south and east has created a vicious cycle for President Hamid Karzai and his international backers: Militants and criminals scare off aid agencies, fueling resentment against the government, especially among ethnic Pashtuns, from whom the Taliban draws its main support.

U.N. spokesman Adrian Edwards said Tuesday's attack "does bring home to all of us the risks of working in this environment."

"The problem, of course, is that insecurity, threats and incidents like this make our job more difficult," he said.

Lex Kassenberg, country director for CARE International, said many people in Afghanistan are "unhappy with the pace of development."

With fighting picking up after a winter lull, aid and development agencies "can become a collateral victim ... and that is a new concern," Kassenberg said.

The Taliban's increasing use of suicide bombers has drawn comparisons with Iraq.

A video obtained by The Associated Press over the weekend purportedly shows a senior Taliban leader, Mullah Dadullah, addressing about 200 young suicide bombers in a walled compound.

"Today, we know better that infidels fear martyrdom attacks more than anything else. They have nothing to resist it," Dadullah told the recruits seated in rows on the ground, some of whom appeared not even in their teens.

He made no distinction between military and civilian targets in the video, which was undated and gave no indication of where it was shot.

There have been 39 suicide attacks in Afghanistan in 2007, a threefold increase from a year earlier, according to Afghanistan's NGO Safety Office, which advises relief groups on security.

Unexploded munitions also remain a danger.

On Tuesday, an old artillery shell exploded outside a school in the western city of Herat, killing four children and wounding five others. Police said children playing in the area may have accidentally triggered the blast.