KANDAHAR, Afghanistan - A suicide car bomber hit a fleet of fuel tankers intended for a NATO base in southern Afghanistan, killing eight Afghans and wounding 21, officials said Saturday.

The attack in Helmand province late Friday burned six fuel tankers parked outside the town of Gereshk, said Dawood Ahmadi, the spokesman for the governor of Helmand. The trucks had been headed to a large NATO base that primarily houses U.S. and British troops.

The attack killed eight Afghan drivers or their assistants, said Abdel Ahad Khan, the Gereshk district chief. Twenty-one people were wounded, he said.

Attacks late last year against U.S. and NATO supply trucks raised concerns that militants were squeezing military supply routes. At the time, U.S. and NATO commanders said they were exploring other ways to bring supplies into the country, including through Russia and the former Soviet satellites that border Afghanistan to the north.

But a spokesman for NATO's International Security Assistance Force said Saturday that there have been few or no attacks on supply trucks in recent months. The spokesman said NATO bases have a lot of spare supplies in the event of attacks.

He said he could not be identified by name because he is not the lead spokesman.

Militant attacks have risen steadily the last three years and have reached a new high. U.S. Gen. David Petraeus said Afghanistan saw 400 insurgent attacks during the first week of June, including ambushes, small-arms attacks, assaults on Afghan infrastructure and government offices, and roadside bomb and mine explosions.

In comparison, attacks in January 2004 were less than 50 per week.