GARDEZ, Afghanistan ? Fierce fighting raged for a fifth day as the United States deployed hundreds of reinforcements Wednesday and gathered 5,000 Afghan troops for an offensive aimed at finishing off al-Qaida.

The U.S.-led coalition mounted punishing, round-the-clock air-strikes above the rugged terrain in eastern Afghanistan, and some U.S. officers predicted the operation could be wrapped up in days.

In Kabul, five peacekeepers two Germans and three Danes were killed in an explosion while trying to defuse anti-aircraft missiles.

The Pentagon said opposition fighters were still putting up stiff resistance after five days of battle, some of it above 10,000 feet in snow-covered mountains. As fighter jets and bombers hit targets, more attack helicopters were called in to boost the firepower in the largest U.S.-led offensive of the 5-month-old war.

U.S. estimates of enemy strength appeared to have been low going into the offensive. Initially, said mission commander Maj. Gen. Frank Hagenbeck, estimates put opposition strength at 150 to 200 fighters. Subsequently, U.S. officers revised those numbers to “the neighborhood of 600 to 700 enemy.”

Defense Secretary Donald Rumsfeld was asked about discrepancy Wednesday and said accurate predictions were impossible going into a battle.

“We’ve been looking at that area for weeks and have a great deal of intelligence information, but it is not possible to have a good count,” Rumsfeld said.

A local Afghan commander, who goes by the single name Isatullah, said U.S. forces received enemy estimates from an Afghan military leader from a different region.

“What were they thinking of getting their intelligence from a commander who was not even from this area?” asked Isatullah, another Afghan commander.

U.S. forces were working with Zia Lodin, an Afghan commander from Logar Province to the north of Paktia Province, where the battle is under way. Lodin had 450 Afghan fighters when the mission began.

The al-Qaida and Taliban forces are armed mainly with mortars, cannons, rocket-propelled grenades, shoulder-fired anti-aircraft missiles and AK-47 automatic rifles.

Afghan soldiers urged residents of the region in Paktia province to turn in al-Qaida warriors, offering a $4,000 reward for each foreign fighter captured alive.

The commander of the operation, code-named Operation Anaconda, said U.S.-led troops had the upper hand after killing hundreds of fighters about half the al-Qaida members holed up in the hills around the village of Shah-e-Kot. U.S. troops were searching their cave hide-outs.

“We own the dominant terrain in the area,” Hagenbeck told reporters Wednesday at Bagram air base north of the capital, Kabul. “We truly have the momentum at this point.”

Gen. Tommy Franks, the U.S. commander in the war in Afghanistan, said he has increased the number of Americans in the operation by 200 to 300 over the past two days, for a total of roughly 1,100.

Afghan allies assist

“I think the days ahead are going to continue to be dangerous days for our forces,” he said in Washington. “But the alternative to taking such a risk is not acceptable.”

About 1,000 or so more Afghans have been fighting alongside the Americans, and their commander said they were also bringing in fresh units, drawing from parts of Paktia, Logar and Ghazi provinces.

“There are 5,000 soldiers collecting in Shah-e-Kot for a final offensive on the al-Qaida to finish them off,” said Ismail Khan, a commander who brought in men from his base in Jaji, northeast of Paktia’s capital, Gardez. “It will be the final push.”

Hagenbeck said more enemy fighters, most of them from Osama bin Laden’s al-Qaida terror network, but also some Afghan Taliban, have been infiltrating the 60-square-mile area battle zone south of Gardez.

“I’m convinced from the evidence I’ve seen that we’ve killed at least half of those enemy forces,” he said. Franks said he had no confirmation of more fighters entering the battle, but did not doubt reports from his field commanders.

Franks said there was no sign of dug-in al-Qaida and Taliban fighters trying to flee the region, which commanders say they have encircled.

The intelligence office of the Paktia government passed out leaflets and made announcements from loudspeakers in Gardez offering $4,000 to anyone who captures an al-Qaida fighter. It appeared the local government was putting up the reward money.

“Dear countrymen: The al-Qaida terrorists are our enemy. They are the enemy of your independence and freedom. Come on. Let us find their most secret hiding places,” the leaflets said.

‘Determined like hell’

In Kabul, Prime Minister Hamid Karzai said the coalition was prepared to take as long as necessary to crush al-Qaida.

“It may be a day or two, or it may take longer,” he said. “We are determined like hell.”

The Pentagon dispatched five Marine attack helicopters to bolster the aerial strike force after Army Apaches were damaged by intense attacks.

One Afghan intelligence officer, who spoke on condition of anonymity, said there were other al-Qaida pockets throughout the eastern mountains besides those targeted by the current offensive.

Operation Anaconda is intended to rout hundreds of enemy fighters believed to have regrouped after the Taliban fell Dec. 7 from their spiritual base in Kandahar. Neither the former Taliban supreme leader Mullah Mohammed Omar nor al-Qaida chief Osama bin Laden was believed to be in the Shah-e-Kot area.

Troops empty caves

U.S.-led infantry units have cleared out several cave hide-outs and al-Qaida compounds, including some where troops found AK-47 ammunition, medicine, night-vision devices and documents including a Saudi identification card.

Eight American servicemen have been killed in the operation so far seven in two attacks on helicopters Monday and another in a ground battle on Saturday, the operation’s first day. They were honored in Germany before their flag-draped caskets were flown back to the United States.

Nine of the American troops injured in recent fighting and a wounded Canadian journalist also arrived in Germany for treatment at a U.S. military hospital.

U.S. intelligence, meanwhile, has learned of plots to conduct car bombings in Kabul against both western interests and the Karzai government, said a U.S. official, speaking on the condition of anonymity.

They were to be conducted by terrorist cells with links to al-Qaida, the official said. It’s unclear what has become of these plots.