Pakistani troops killed 18 militants in a fresh offensive Tuesday against insurgents blamed for a wave of recent bombings in the main northwestern city of Peshawar.

The operation in Bara region was the latest salvo in a broadening campaign against Al Qaeda and the Taliban in the lawless lands close to the Afghan border since last year.

Authorities claim hundreds of militants have been killed, yet the assaults do not appear to have dented the insurgents' ability to strike.

Maj. Fazlur Rehman, a spokesman for the paramilitary Frontier Corps, said ground troops, helicopters and artillery were being used in the operation in Bara close to Peshawar.

The aim of the assault was to capture mountain heights and strategic locations from the militants who had been attacking Peshawar, he said, adding 18 militants had been killed.

Peshawar and surrounding areas have seen a relentless wave of bombings in recent weeks that have killed more than 150 people. The attacks are apparently aimed at avenging an ongoing, major army operation in South Waziristan, a main militant hub 167 miles from Peshawar.

Pakistan is under pressure to crack down on militants and has won praise from its Western allies for the South Waziristan offensive. But critics say the army should do more against insurgent groups who use the northwest as a safe haven to attack Western troops in Afghanistan.

Journalists are banned from visiting the border region, making it impossible to verify casualty figures.