At least 55 people have been killed and nearly 100 injured in a suicide bomb attack on a mosque in northwest Pakistan, local officials say.

The blast occurred in Darra Adam Khel, a suburb of Peshawar, the capital of the Khyber-Pakhtunkhwa province, during Friday prayers, the most attended prayer session of the week.

Hours later, grenades thrown into a second mosque, near Peshawar, killed at least two people.

It was not immediately clear who carried out the attacks, the latest in a series of mosque and shrine bombings.

U.S. State Department spokesman Mark Toner condemned the two attacks, saying they "brutally targeted innocent people" at places of worship.

compiled from agency reports