Coalition forces are moving aggressively against al-Qaida and Taleban forces dug into the mountains of eastern Afghanistan.

Senior Pentagon officials say there has been some softening of resistance from al-Qaida and Taleban forces following relentless allied bombing attacks and a steady advance by ground troops.

But while there have been scores of enemy casualties, chief Pentagon spokesperson Victoria Clarke says the operation, dubbed Anaconda, is far from over. She said hundreds of well-armed, hostile fighters are still entrenched in positions in the mountainous terrain.

"We have always said that the further this went on, the harder it would get," noted Ms. Clarke. "The people who are left fighting, the al-Qaida, are among the toughest, most violent, the most committed to fighting this out to the end."

Pentagon officials say no one on the al-Qaida and Taleban side has tried to surrender since the operation began late last week. Only four prisoners have been taken so far.

In one cave complex formerly held by al-Qaida forces, allied soldiers have found mortars, rocket-propelled grenades and small arms, At another location, the Pentagon reports finding more weapons and ammunition along with foreign passports and drivers licenses.

The operation is the biggest in the five-month-old war in Afghanistan. Australian, Canadian, Danish, French, German and Norwegian forces are backing up the American and Afghan troops taking part.