Peshawar, Pakistan - At least 30 people were killed and more than 140 wounded when a powerful bomb ripped through a crowded mosque in the Pakistani city of Peshawar, police said.

The blast is assumed to be a result of a suicide bombing, but the investigation is ongoing, police in the northwestern city said, adding the carnage took place during afternoon prayers.

The attack took place inside a high-security zone next to a police headquarters.

It is believed that a significant number of police officials were among the victims, but the exact figure was not yet known, city police chief Muhammad Ijaz said.

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No group has claimed responsibility.

Asim Khan, a spokesperson for the Lady Reading Hospital, the biggest health facility in the city, suggested the death toll could rise, saying more than a dozen of the injured were in critical condition.

The hospital is appealing for blood donations.

Local media aired footage of the damaged mosque as rescuers tried to find people potentially trapped under the rubble. A portion of the building had collapsed and the roof caved in.

Prime Minister Shehbaz Sharif condemned the bombing and said that the attackers behind the incident "have nothing to do with Islam."

"Terrorists want to create fear by targeting those who perform the duty of defending Pakistan," he said.

The death toll in the bombing attack in Pakistan has risen to at least 32 people, with some 150 others injured. The majority of the people confirmed dead are members of the police force, a hospital spokesperson told dpa.

Many of the wounded with minor injuries were discharged from the hospital, Asim Khan, a spokesperson of the Lady Reading Hospital told dpa. Khan suggested the death toll could rise even higher.

Peshawar’s police chief said that the capacity of the main hall of the mosque was nearly 300, and it was nearly packed to capacity at the time of the explosion.

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"At least five people were still strapped under a portion of a collapsed roof, and we are trying to save their lives," Bilal Faizi, a spokesperson for provincial rescue department said.

A police officer who survived the attack told Geo News that the explosion took place the moment prayers started. "It was a powerful explosion. There was smoke everywhere after the blast," he said.

At least 59 people have now been confirmed dead from the powerful suicide attack, with a further 157 injured, according to officials citied by ABC News.

The attack was one of the country's deadliest in years.

A leader of the Pakistani Taliban, also known as Tehreek-e-Taliban Pakistan or TTP, claimed responsibility for the attack in a post on Twitter.

Yet later, a TTP spokesperson claimed the group had no part in the bombing.

An inquiry will be conducted into how the multi-layered security infrastructure at the site was breached, Interior Minister Rana Sanaullah said.