Huge V-winged aircraft carrying U.S. Army troops touched down at Kandahar's airport Saturday, as the rotation of U.S. forces in Afghanistan gathered speed. Marines still holding the battle-pocked base commemorated comrades killed in an air crash.

Col. Frank Yiercinski of the 101st Airborne Division said at least 2,000 troops would be flown to Kandahar over the coming days. While the approximately 3,000 U.S. Marines now holding the airport were primarily there to secure it, the U.S. Army would perform a "full spectrum" of operations during its open-ended stay, possibly including humanitarian assistance, he said.

Asked about Thursday's attack on the airport by unknown fighters, Yiercinski said: "This is still a dangerous place."

The fighters opened fire as the first planeload of Al Qaeda and Taliban prisoners left the airport base for the U.S. Guantanamo Bay Naval Station in Cuba and triggered an intense 40-minute gunbattle, the first on the base since the Marines dug in a month ago.

Deteriorating security throughout the province is a growing concern. Not only are many Taliban and Al Qaeda fighters possibly still in the province, but local tribal leaders frequently distrust each other and are believed to hold weapons stockpiles against future interethnic conflict.

Journalists traveling into the province from Pakistan frequently complain of shakedowns at the border. Afghan fighters backed by U.S. special forces sealed a key border crossing into Pakistan on Friday in an apparent attempt to keep tribesmen from bringing weapons into the war-scarred country. A spokesman for regional governor Gul Agha said Friday that the disarmament efforts in Spinboldak were also aimed at ending the practice of demanding bribes for passage from outsiders.

About a dozen U.S. special forces were among the 30-vehicle convoy that came to Spinboldak and included Agha and his fighters. Agha intends to name a new leadership for Spinboldak after which the various local factions are to turn in their weapons.

Agha's forces also closed the crossing point about 10 miles south of here at the Pakistani town of Chaman.

Also near the Pakistani border but further north, villagers in Khost said Saturday that U.S. planes dropped bombs on the region overnight, and a resident who identified himself only as Mohammed said 14 people were killed by bombs Thursday. Khost province governor Bacha Khan said special forces were seen in the region and had arrested four of his people.

"We want them released," he said. "They are not Al Qaeda, they are not Taliban."

The Pakistan-based Afghan Islamic Press also said U.S. planes bombed the Zhawar area in Khost province late Friday and early Saturday. U.S. planes have over the last few days targeted camps that were being used by Al Qaeda, sources said.

Khan said the Zhawar region contains cave complexes larger than those at Tora Bora.

Security in Kabul, the capital, also has been threatened by the presence of armed men on the streets. Friday midnight was the deadline for meeting Prime Minister Hamid Karzai's order that all armed men return to their barracks.

Although there was a noticeable reduction in the number of men carrying Kalashnikov machine guns and of vehicles packed with armed men, guns remained a common sight.

Besides the attack on the airfields, the Marines also have been shaken by an air crash that killed seven of their comrades — the highest single American casualty toll of the Afghan campaign.

On Saturday, while U.S. and Pakistani forces continued scouring the remote mountain region of the crash, about 100 solemn-faced Marines gathered at their Kandahar base to pay tribute to the victims, who died Wednesday, when their KC-130 aircraft slammed into a mountain ridge near the Shamsi air base in southwestern Pakistan.

The deaths will "strengthen our resolve to do everything we can to eradicate terrorism in the world," said Cmdr. Joseph Scordo, a Marine chaplain, to Marines assembled in the bullet-pocked airport terminal with their M-16 assault rifles and rocket launchers pointed at the floor and singing "Amazing Grace."

In other developments:

—The U.S. State Department announced that Secretary of State Colin Powell will visit Afghanistan next week to show support for the pro-Western interim government installed three weeks ago.

—Afghanistan's national airline, banned internationally more than two years ago, and the country's central bank will be allowed to operate again, the U.S. ambassador to the United Nations said.