PESHAWAR, Pakistan (AP) — A suicide bomber struck Monday inside a mosque within a police compound in the northwestern Pakistani city of Peshawar, killing at least 28 people and wounding as many as 150 worshippers, most of them policemen, officials said.

The bombing drew nationwide condemnation from opposition political parties and government officials. Ghulam Ali, the provincial governor in Khyber Pakhtunkhwa, where Peshawar is the capital, said there were fears the death toll could rise even further.

Most of the casualties were policemen and police officers — the targeted mosque is located within a sprawling compound, which also serves as the city’s police headquarters. Police said between 300 to 350 worshipers were inside the mosque when the bomber detonated his explosives.

No one immediately claimed responsibility for the bombing, said Saddique Khan, a senior police official in Peshawar, but the Pakistani Taliban have been blamed in similar suicide attacks in the past.

The police compound is located in a high-security zone in Peshawar, along with several government buildings, and it was unclear how the bomber managed to penetrate so deep inside the zone unnoticed.

The impact of the explosion collapsed the roof of the mosque, which caved in and injured many, according to Zafar Khan, a local police officer.

A survivor, 38-year-old police officer Meena Gul, said he was inside the mosque when the bomb went off. He said he doesn’t know how he survived unhurt. He could hear cries and screams after the bomb exploded, Gul said.

Rescuers scrambled trying to remove mounds of debris from the mosque grounds and get to worshippers still trapped under the rubble, police said. At a nearby hospital, many of the wounded were listed in critical condition as the casualty toll rose.

Prime Minister Shahbaz Sharif in a statement condemned the bombing, and ordered authorities to ensure the best possible medical treatment to the victims. He also vowed “stern action” against those who were behind the attack.

Former Prime Minister Imran Khan also condemned the bombing, calling it a “terrorist suicide attack” in a Twitter posting. “My prayers & condolences go to victims families,” said the ex-premier. “It is imperative we improve our intelligence gathering & properly equip our police forces to combat the growing threat of terrorism.”

Peshawar has been the scene of frequent militant attacks. The Pakistani Taliban, are known as Tehreek-e-Taliban Pakistan or TTP, and are separate group but also a close ally of the Afghan Taliban, who seized power in neighboring Afghanistan in August 2021 as U.S. and NATO troops were in the final stages of their pullout from the country after 20 years of war.

The TTP has waged an insurgency in Pakistan over the past 15 years, fighting for stricter enforcement of Islamic laws in the country, the release of their members who are in government custody and a reduction of the Pakistani military presence in the country’s former tribal regions.

Pakistan has witnessed a surge in militant attacks since November when the Pakistani Taliban ended their cease-fire with government forces.

The truce ended as Pakistan was still contending with last summer’s unprecedented flooding that killed 1,739 people, destroyed more than 2 million homes, and at one point submerged as much as one third of the country. The flood damages totaled to more than $30 billion and authorities are now, months later, still struggling to arrange tents, shelter and food for the survivors.

Cash-strapped Pakistan is currently also facing one of the worst economic crisis and is seeking a crucial installment of $1.1 billion from the International Monetary Fund — part of its $6 billion bailout package — to avoid default. Talks with the IMF on reviving the bailout have stalled in the past months.

Sharif’s government came to power last April after Imran Khan was ousted in a no-confidence vote in Parliament. Khan has since campaigned for early elections, claiming his ouster was illegal and part of a plot backed by the United States. Washington and Sharif have dismissed Khan’s claims.