Operation Medusa was launched in Panjwayi district of southern Kandahar province -- the spiritual and symbolic heartland of the Taliban movement -- after residents had been warned for days to leave the area, officials said.

It involved "hundreds" of Nato troops and a similar number of Afghan police and army soldiers, a spokesman for Nato's International Security Assistance Force (Isaf) said.

Isaf only deployed to southern Afghanistan a month ago and this operation is its biggest against the insurgents.

Panjwayi, about 35km west of Kandahar city, has seen months of intense fighting, with ISAF officials saying it has one of the biggest concentrations of Taliban in southern Afghanistan.

Seasoned Taliban fighters in the area had been "hardening their defence positions and sandbagging buildings and bringing in ammunition," spokesman Major Scott Lundy said.

"We have had indications that these Taliban fighters are of the hardcore variety as opposed to the soldiers-for-a-day we see sometimes," he told AFP.

The area, from where the extremist Taliban emerged and took up arms in the early 1990s to eventually control most of Afghanistan by 1996, is also near a key east-west route that has seen several deadly attacks on foreign forces.

"The goal is to remove the Taliban threat from Panjwayi and stabilise the situation so that much needed reconstruction and development projects can resume," Lundy said.

Isaf and Afghan officials had urged residents through the local media and meetings with area elders to leave before the offensive started, he said.