Tora Bora Cave War Continues

US Defence Secretary Donald Rumsfeld is the first senior American official to visit since Afghan and US forces toppled the Taliban. Rumsfeld has been on a "thank you" tour of the region, but his visit to Afghanistan was kept a secret until the last moment.

He arrived at Bagram Airbase near Kabul, where he sat down to talks with Hamid Karzai, who will head an interim government which takes power next week.

"It's important to have a chance to sit down face to face and talk about what's been done and what's left to be done," he told reporters. "There's a good deal left to be done and I want to make sure that we are all on the same wavelength."

Earlier, US intelligence agencies had picked up the voice of Osama bin Laden on a short wave radio. His voice was recognised by an array of electronic devices used by special forces on the ground, spyplanes and eavesdropping satellites.

Evidence that the terrorist leader has been personally directing al Qaeda forces in Tora Bora is the first positive lead in the search for bin Laden. It is widely believed that he is making his last stand in the caves of Tora Bora now under siege by Afghan, American and British forces.

But his actual whereabouts remained a mystery. "I'm going to wait and see where he is. I've received nothing that is discouraging. We continue to receive mixed messages," Rumsfeld said.

Meanwhile B-52 bombers filled the skies on the first day of the Eid al-Fitr festival that celebrates the end of the holy fasting month of Ramadan, dropping huge bombs on suspected al Qaeda positions through the night and into the morning.

On the ground, special forces troops are closing in on al Qaeda hide-outs. US forces have also found materials and documents at a former al Qaeda base in southern Afghanistan and they were being tested for chemical, biological and radiation content.

Rumsfeld said the site was on a list of places to be searched. But the take from this one was "particularly large and significant", he said.