PESHAWAR Pakistani forces have killed 25 suspected militants in a two-week operation to secure the frontier city of Peshawar, which sits on a key supply route for U.S. and NATO troops in Afghanistan, an official said on Monday.

Security forces backed by warplanes and artillery have swept through an area between the city and Pakistans wild tribal belt, where Taliban and al-Qaida militants have found refuge.

Zafrullah Khan, commander of paramilitary Frontier Constabulary troops in the area, said his force and police have taken control of 22 of 25 targeted villages and would clear the others within a week.

The militants in these areas have been a big threat to the writ of the government, Khan said. They have been a main source and origin of the crimes in Peshawar and other cities of the province.

Some 25 suspects have been killed and another 35 arrested during the operation, he said. He said those detained included foreigners, but provided no details.

Four suicide jackets as well as weapons including guns, rockets and grenades were seized, he said.

Rising violence in the northwest, including the shooting death of an American aid worker in Peshawar, have heightened concern that the city itself is under threat.

Pakistani troops have been battling Taliban militants in Bajur, a nearby tribal region, since August. The fighting has spread to neighboring Mohmand, which borders the villages targeted in the sweep near Peshawar.

The city is a vital hub for military and relief efforts in Pakistans northwest as well as lying on a supply route for foreign troops fighting in Afghanistan.