Three warship-based Marine Harrier jets bombed a target in southern Afghanistan Monday as tribal and other opposition fighters supported by U.S. warplanes pressed for control of the last Taliban stronghold of Kandahar, from which the United Nations says thousands of refugees have fled.

Capt. David Romley said he did not have details of the Harrier jet's target. He said the strike was called by a forward observer other than the U.S. Marines, who turned a desert airfield about 70 miles southwest of Kandahar into a forward base over a week ago.

Romley told reporters the Harrier fighters "hit their targets" with 500-pound bombs.

The jets are based on the amphibious landing ship USS Peleliu, the lead ship of a six-vessel task force in the Arabian Sea. The Marines in Afghanistan also are coming from the Peleliu and from the USS Bataan.

It was unclear if the Harrier strike was linked to the fight for Kandahar, the last stronghold of the Taliban militia.

Waves of U.S. warplanes pounded the southern Afghan city, which Taliban supreme leader Mullah Mohammed Omar has vowed to defend to the death.

A military source at the Marine base said on condition of anonymity that the Taliban had moved reinforcements into Kandahar from Lashkargah, a town west of Kandahar.

One Pashtun tribal commander with forces near Kandahar claimed that hard-line foreign Al Qaeda troops, loyal to prime terrorist suspect Usama bin Laden, were stopping demoralized Afghan Taliban troops from surrendering. Another tribal force said it was closing in on Kandahar airport.

U.N. High Commissioner for Refugees spokesman Peter Kessler estimated that 8,000 Afghans have reached the safety of neighboring Pakistan since the conflict intensified last week. Other refugees have fled north to the capital, Kabul.

Those who have arrived at the Pakistan border outpost of Chaman talked of chaos and fear in Kandahar as well as on the roads east to Pakistan. Conditions in and around Kanadhar were unclear Monday and reports of clashes among rival forces could not be verified. The Taliban refuse to allow foreign journalists into the areas they control.

"From night until morning the planes have been coming. Every minute I was on the road I was afraid," said one man, who identified himself only as Mahmood.

Arab satellite television Al-Jazeera quoted Molloy Obeid Allah, who governs a nearby Taliban-controlled town of Spinboldak, as saying Taliban forces had blocked some opposition fighters from advancing on Kandahar.

In contrast, tribal forces said they had overcome and captured Taliban troops in the same area. The claims from either side could not be independently verified.

Hamid Karzai, a powerful Pashtun tribal leader, said Monday his forces were 18 miles north of Kandahar and had met no resistance

"There has not been any fighting. We have intentionally not launched any attack because we want to take the city without any fighting," he said by satellite telephone.

"There have been some surrenders of Taliban soldiers," he said, adding that the backbone of the Kandahar's defenses appeared to be made up of mainly Arab Al Qaeda warriors.

He claimed they were preventing Kandahar's Afghan Taliban force from capitulating.

"They can't get out of the city to surrender. The Arabs have blocked the exits of Kandahar," he said.

A tribal spokesman, Khalid Pashtun, said anti-Taliban forces, loyal to former Kandahar governor Gul Agha were moving from the south and east toward Kandahar and some fighters were near the perimeter of its airport on Monday.

"We have almost reached it," Pashtun said by satellite telephone. "Our forces are advancing. The Taliban and Arab forces are retreating from the airport."

He predicted forces of tribal leader Gul Agha would seize the airport within a day or two.

He said as many as 50 airport defenders died in overnight bombing, but said tribal forces had suffered no casualties. His report could not be confirmed.

The Associated Press contributed to this report