A Pakistani official says thousands of people have been displaced over the past week after the military launched an operation against militants in a tribal area in the country's northwest.

Mujahid Hussain, chief of disaster management efforts in the Kurram tribal area, said on Wednesday that the families left their villages because of the fighting. He says he estimates that between 35,000 and 49,000 people have been displaced.

Most of those who fled are staying with relatives but Hussain says tents would be set up for those who have nowhere to go in a refugee camp near the city of Parachinar.

Kurram is one of seven Pakistani tribal regions near the Afghan border. They are very volatile areas and the Pakistani military has launched numerous operations against militants there.