ORA BORA, Afghanistan, Dec. 5 — A front-line anti-Taliban commander said today that Osama bin Laden's top aide, Ayman al-Zawahiri, had been killed during fierce fighting here.
"This morning I got the news from my commanders in the mountains," said the Afghan commander, Aleem Shah. "Zawahiri is dead." There was no independent means to verify this assertion, and military officials in Washington said they had no confirmation of his death.
Reports that Mr. Zawahiri might have been killed or injured by American bombing have circulated for several days, but the account from the front-line commander appeared one of the more credible. He said he had no information on any other deaths among Al Qaeda leaders.
Today, Afghan fighters began their first assault on Mr. bin Laden's mountaintop redoubt. The Afghans, advised by a small group of United States Special Operations troops operating near Jalalabad, fought a battle against Mr. bin Laden's Al Qaeda forces at Tora Bora, at the edge of snow-capped mountains cresting at Pakistan's border.
Snow has fallen steadily here, apparently making it impossible to use the mountain passes into Pakistan that might have provided Mr. bin Laden with one means of escape, if he was indeed in the area.
Mr. bin Laden and Dr. Zawahiri, who is credited with the organizational skill behind Al Qaeda's attacks on American targets, including the deadly Sept. 11 suicide hijackings, have been inseparable since 1998. That year, Al Qaeda formed an alliance with the group that Dr. Zawahiri had led since the late 1970's, the Egyptian Islamic Jihad. From then on, Al Qaeda's attacks escalated in skill, secrecy and savagery.
The Afghan commanders directing today's attacks said Al Qaeda's days in hiding in the caves and canyons of Tora Bora were numbered.
"Half of Tora Bora is under our control," said Commander Shah, directing fire from three aging Soviet T-56 tanks. "Upward in the higher ridges is Al Qaeda."
He directed his troops from a bluff looking south to Tora Bora, a jagged landscape of ridges rising from the Maleva Valley and overlooked by the White Mountains. The ridges and the valley have been bombed repeatedly by the United States for five days.
The mountain peaks can only be traversed by foot or mules, and their passes into Pakistan, a network of old smugglers' trails, became snowbound Monday night.
It is uncertain whether Mr. bin Laden himself is hiding in the caverns carved into the mountains here with the Central Intelligence Agency's help during the Afghans' war against the Soviets in the 1980's. Commander Shah's superior, Hazarat Ali, the security minister of the self-proclaimed government in this area, said Mr. bin Laden was last seen in Tora Bora on Friday, when American bombers began a series of night-and-day attacks on the hide- out.
Assisted by American B-52 bombers, whose payloads sent mushroom clouds of smoke and dust rising hundreds of feet into the mountain air, the Afghans were using artillery and hundreds of foot soldiers to try to flush out some 2,000 fighters loyal to Mr. bin Laden.
The American bombing of Tora Bora has been aimed at forcing the Al Qaeda fighters into smaller groups whom the Afghan forces can engage in battle.
Some one thousand Afghan troops were at the front Tuesday night, said Hazarat Ali, the main military commander of the Eastern Shura, which overthrew local Taliban leaders 20 days ago. He said another 2,000 would be assembled for the fight against Al Qaeda at Tora Bora, which he described as "a wild kind of area."
The Afghans' strategy was apparent at Tora Bora today.
"We are trying to surround them," Commander Shah said. "There is no opportunity for them to cross into Pakistan. The passes are snowed in."
Mr. Ali, his superior, said: "We will follow our own strategy of guerilla warfare. If we have to cut off their food and water, we will do that."
The chief intelligence officer for the region's anti-Taliban forces, Sohrab Qadri, added, "We have blocked all of the roads."
The fighting today was fierce, Mr. Qadri went on, saying, "Their resistance is hard, very tough."
The local Afghan forces took control of the road from Jalalabad, the provincial capital, to Tora Bora on Monday, after the American bombing of villages along the way. The bombing, which the United States aimed at Al Qaeda command and control centers, also hit civilian targets, villagers and independent witnesses said.
Since the fall of the Taliban, the foreigners who supported the former government and form the core of Al Qaeda have become the object of particular hatred for many Afghans, including the forces involved in the offensive here.
About twenty American Special Operations troops have been working in the Jalalabad area for about two weeks. They are not visible, but their number is increasing, as evidenced by two helicopter landings over the weekend, one carrying cargo, the other carrying men who hopped into eight light trucks provided by Mr. Ali, according to airport guards who witnessed the landings.
They are providing targeting information for American bombers and some strategic and tactical assistance to the Afghans, American military officials said.
Plumes of smoke from shells and bombs rose among the dark purple ridges at midday as a B-52 bomber passed over the mountains, its distinctive four contrails white against a flawless blue sky.
Commander Ali himself was seen at the head of a column of pickup trucks, carrying rocket-propelled grenade launchers, racing up the bumpy dirt road southward toward the front, past herds of camels and goats, past newly sown opium poppy fields and a sign reading, in English, "Welcome to a drug fre (sic) Afghanistan."
In the other direction, headed north, villagers fleeing the bombing plodded toward Jalalabad with bedding, carpets, bags of clothing and bundles of firewood piled atop donkeys, their cattle sometimes blocking the military traffic.
Meanwhile, Commander Shah directed the battle by walkie-talkie.
"We are trying our best to take them alive," he said. "We are trying to surround them. If we find them alive, well and good.
"But this is war, and we want to finish them," he added.
Asked if he thought Mr. bin Laden was holed up in the caves of Tora Bora, Commander Shah replied: "We don't have complete confidence Osama is there. We are sure that Al Qaeda and the Arabs are."
And, he added, he was confident that Dr. Zawahiri had been killed.
Dr. Zawahiri, 50, was a young surgeon in Cairo when he devoted his life to radical Islamic causes in the late 1970's. He became one of the world's most wanted terrorists.
American authorities believe he masterminded the Sept. 11 attacks on the United States.
In 1999, he was indicted in New York for the bombings of the American embassies in Kenya and Tanzania, which killed 224 people, including 12 Americans. He is under a death sentence in Egypt for his terrorist actions against the state.
His death, if true, would be a crippling blow to Al Qaeda.
He is believed to have furnished much of the organizational skill that built Mr. bin Laden's organization into a kind of holding company for international terrorism. Al Qaeda's third-in-command, Muhammad Atef, was killed in American bombing raids outside Kabul.
