GARDEZ/BAGRAM AIR BASE, Afghanistan: Hundreds of US troop reinforcement, loaded with equipment to attack caves, were airlifted into mountain battlefields in east Afghanistan on Wednesday prepared for a dangerous lengthy hunt for die-hard al-Qaeda and Taliban fighters.

A US military official said on Wednesday the US-led forces had killed half the Taliban and al-Qaeda fighters holed up in snow-capped mountains near the heavily fortified town of Gardez, capital of Paktia province, in attacks that began last week. "We've killed up to 500 or more," said Lt-Col Walter Piatt at Bagram.

Commander of the military operation, codenamed Anaconda, Maj-Gen Frank Hagenbeck said: "In the last 24 hours, we've got confirmed kills in the hundreds.". He said the US-led coalition had been up against al-Qaeda fighters "somewhere in the neighbourhood of 600 and 700" and was "convinced from evidence we killed at least half of those".

Hagenbeck said the US-led forces had been involved in "intermingled and close combat" and had in the past two days come within 50 meters of the enemy. Eight US troops and seven Afghan soldiers have died in the operation and 48 US servicemen were wounded in the latest action but half of them were already back in action, Hagenbeck added.

In his first remarks on the progress of the US-led attack of the five-month-old Afghan war, interim Afghan leader Hamid Karzai said the offensive was succeeding despite the heaviest American casualties of the conflict. Asked by Reuters on the fifth day of Operation Anaconda was going, he said: "Successful, successful."

US military officers in the battlefield spoke of stiffer resistance than expected. Afghan soldiers returning to Gardez from the frontline said the rebels were making hit-and-run attacks on the combined US-Afghan force of 1,500 besieging their caves and bunkers. "They are fighting a guerrilla war," Muhammad Yunis told Reuters. "They have divided into groups of four or five. They jump out of a cave, open fire on us and then dart back into the cave or move to another one. They know the area very well."

Reuters correspondents in Gardez said they could see little US bombing of the area now, indicating aerial attacks were being held back to allow ground troops into the area. Overnight, the US Chinook helicopters took off from Bagram, a Soviet-built complex about 50 km north of Kabul. Some troops carried shoulder-launched rockets, crucial to blasting forces out of snow-covered cave entrances.

Afghan officials believe neither Saudi-born al Qaeda leader bin Laden nor Taliban leader Mulla Muhammad Omar are in the battle area. US Major Bryan Hilferty told Reuters at Bagram there had been a major movement of troops from the present main US base near Kandahar to Bagram and said there were around 1,000 US troops actively involved in the battle. Some 200 commandos from Australia, Canada, Denmark, France, Germany and Norway are also on the ground, backed by several hundred Afghans under the command of local Afghan warlord Zia Lodin. Zia's support "turned out to be absolutely crucial to us", Gen Hagenbeck said.

US defence officials told Reuters the US forces this week moved Marine Corps AH-1 Cobra attack helicopters into Afghanistan along with Army AH-64 Apaches, already used in the operation.

The resurgence of fighting followed a lull of several weeks in which some Washington politicians questioned the US campaign's success. Fears have been raised that the country will fall back into the warlordism and anarchy that reigned before the rise of the Taliban.

Afghan Defence Minister Muhammad Qasim Fahim on Wednesday ended a two-day meeting with warlords from all over the country whom he summoned to Kabul to discuss the security situation. The meeting was also attended by a local Gardez commander, Ziauddin, who later said Saif-ur-Rahman Mansoor, who is leading the battle against the US troops in eastern Afghanistan had tried to resolve his dispute with the interim government, peacefully.

Mansoor had sent a letter to Fahim, seeking a peaceful solution to the disputes and offered to hold talks "to end his armed defiance of the interim administration" in Kabul, Ziauddin said.

Ziauddin also denied that militants from Osama bin Laden's al-Qaeda network were based in the mountain hideout, saying all of the fighters with Mansoor were Afghans. Ziauddin said the US forces had suffered their heaviest casualties of the Afghan campaign because they did not fully consult the interim government before launching the operation. "The Americans did not have much consultation with the interim administration. They went by themselves," Ziauddin said.

Ziauddin said Mansoor, a former Taliban commander, commanded most of the fighters in the snowy mountains, where he has lived since the 1980s war against the Soviet occupation. "Mansoor had a base in the Arma mountains, even during the war against the Russians and at the time no one managed to defeat him there. It is a very dangerous area," Ziauddin said.

With competing warlords threatening the peace, the United States and its allies are considering doubling the number of foreign peacekeepers, perhaps under the US command, diplomats at the United Nations said.

So far the international security force in Afghanistan has been confined to Kabul and its environs, with 4,500 troops, despite pleas from Karzai, head of the UN-backed interim government, to expand the force to other cities.

The international peacekeepers said they had received credible intelligence reports about plans to kidnap a foreign journalist in retaliation for the Gardez attack.

Meanwhile, two German and three Danish soldiers were killed, while, defusing explosives in Kabul on Wednesday. The five were killed and another seven injured when two Russian-type SA-3 anti-aircraft missiles went off unexpectedly, during explosives clean-up work in the Afghan capital, the chief of the German armed forces Harald Kujat said, describing it as a "very tragic accident".

Kujat said in Berlin that it was not immediately clear why the munitions, which had been taken to a field used for defusing explosives, detonated prematurely. He said preliminary findings did not indicate any violation of security guidelines and vehemently dismissed speculation by reporters that the soldiers had been poorly equipped for the operation.

Some 860 German soldiers are currently serving with the 4,500-troop ISAF. They have been tasked in particular with mine removal, munitions defusal and police duties. Dutch and Danish soldiers are stationed with the German contingent, which is to number up to 1,200 troops by the end of April.