A bomb explosion inside a Sunni Muslim mosque on Saturday killed four people and wounded 28 others in Pakistan's northwestern city of Peshawar, officials said.
The explosion took place while people were saying afternoon prayers in the mosque located in the densely populated Mohalla Baqar Shah area of Peshawar city.
"The bomb, which was planted inside the mosque went off killing four people and wounding 28 others," senior local police official, Imran Shahid, told AFP.
He said that there were up to 40 people present in the mosque at the time of the explosion.
A spokesman for Peshawar's Lady Reading Hospital, Jameel Shah, also confirmed the casualties: "We have received four dead bodies and over 20 wounded people, and the condition of two patients is very serious."
Peshawar is vulnerable to bomb blasts and Taliban attacks as it runs into the semi-autonomous tribal belt, considered a safe haven for Taliban, Al-Qaeda and other insurgents fighting both in Pakistan and across the border in Afghanistan.
The attack came just six days after a car bomb killed 50 people in a mainly Shiite Muslim neighbourhood of Karachi, the fourth in a series of major attacks on the minority Shiite community since January 10 that have killed more than 250 people.
Pakistan's parliament is due to dissolve in less than two weeks in preparation for elections. But rising violence has raised serious questions about security.
Pakistan says 35,000 people have been killed as a result of terrorism since the 9/11 attacks and the 2001 US-led invasion of Afghanistan.