PESHAWAR, Pakistan — Dozens of suspected militants attacked a major power station in northwest Pakistan with mortars and rocket-propelled grenades and killed seven people, police said on Tuesday.

The assault, in the run-up to May 11 general elections, destroyed the biggest power station in Khyber Pakhtunkhwa province, suspending electricity supply to half of the major city of Peshawar.

It served as a reminder that Pakistan's leaders have failed to tackle a Taliban insurgency that remains potent despite a series of security crackdowns.

Pakistan's Taliban, which is close to al-Qaida, has threatened to escalate violence ahead of the polls, including attacks on political rallies.

Police official Mohammad Ishaq said two people, a policeman and a security guard, were killed on the spot in the pre-dawn incident and five others died later after being kidnapped.

The bullet-riddled bodies of the captives have been recovered, the official added. There was no immediate claim of responsibility.

"They entered the grid station and started setting ablaze each and every thing. They kidnapped nine people and killed five of them later and threw their bodies in the fields," Ishaq said.

Four Water and Power Department employees who were kidnapped were still missing, he said.

The militants traveled to the grid from a nearby Taliban stronghold, Darra Adam Khel, said the police official.

The militants had destroyed the entire grid station, said Shaukat Afzal, a spokesman of the Peshawar Electric Supply Company.

"People may face some extra power load shedding in the coming days," he added.

Pakistan's military has failed to break the back of the Taliban, despite numerous offensives against their strongholds in the semi-autonomous tribal areas near the Afghan border.