US drones regularly attack hideouts of the militants in Pakistan's tribal region.

The US has intensified drone attacks on the tribal regions despite Pakistan's protest at a time when the security forces are engaged in a major offensive against Mehsud in South Waziristan.

Pakistan insists that drone attacks are counterproductive and must be stopped but US officials have ruled out any change in the policy.

Pakistani officials say the drone strikes have killed more than 400 people in more than 40 attacks since August 2008.