ISLAMABAD—Dozens of suspected Taliban militants destroyed an electricity station in northwestern Pakistan, killing at least seven people and disrupting power supply to the area, officials said.

The predawn assault Tuesday blew up the power station on the outskirts of Peshawar, capital of the Khyber Pakhtunkhwa province along the Afghan frontier. Noor Bashar, a local police officer at the Budha Berh police station, put the number of assailants at more than 40.

Pakistani Taliban extremists, who work closely with al Qaeda and operate independently from the Afghan Taliban, are based in parts of the lawless tribal areas close to Peshawar. Their campaign of violence, focused most on this predominantly Pashtun province, appears to be escalating in the run-up to national elections slated for May 11.

Shaukat Afzal, spokesman for the Peshawar Electric Supply Co., said the attackers struck at around 2 a.m. "from different angles." "They attacked our grid station, set it on fire, smashed things up and then planted bombs, which they detonated," said Mr. Afzal.

He said that four employees of the electricity company were killed, along with three police officers. Four other employees had been "taken away" by the attackers, he added. The bodies of five victims were found in nearby fields, where they apparently had been dumped upon fleeing the scene, Mr. Bashar said.