The casualties and refugees were from Panjwayi and Zhari districts, alleged Taliban strongholds in southern Kandahar province where Afghan and Nato-led troops launched Operation Medusa on September 2.

Nato's International Security Assistance Force (Isaf) says it has killed more than 500 insurgents and acknowledges there have been some civilian casualties although it says it is investigating how many.

People fleeing the battles and officials from the area had reported that between 30 and 40 civilians had been killed, mainly in bombardments, said human rights official Shamsuddin Tanwir.

Although the government and Isaf had warned them to leave the area before Medusa was launched, many had not had enough time to do so, said Tanwir, from the Kandahar office of the Afghanistan Independent Human Rights Commission.

Isaf dropped leaflets over the area informing people of the planned action and used local media and government officials to pass on the message.

Tanwir said his office planned to send people there once the operation was over to try to verify the numbers.

Panjwayi and Zhari are about 35km west of Kandahar, the biggest city in southern Afghanistan.