At least four people were killed in a US drone attack in the North Waziristan tribal region on Wednesday, report said. The drone fired two missiles on a vehicle in the tribal regions Dattakhel area. The deeply unpopular covert US drone campaign, which operates with the tacit consent of Pakistani officials, has been ramped up recently as the missiles target insurgents believed to be hiding in the lawless border regions. Missile attacks doubled in the area last year as the covert campaign was stepped up, with more than 100 drone strikes killing over 670 people in 2010 compared with 45 strikes that killed 420 in 2009, according to a foreign news agency tally.