An explosion has ripped through a Shia mosque on the outskirts of Pakistan’s capital during Friday prayers, killing 31 people and injuring at least 169 others, according to officials. Police said they were investigating whether the attack was carried out by a suicide bomber.

There were fears the death toll from the blast at the Khadija al-Kubra mosque in Islamabad could rise as some of the injured were reported to be in a critical condition. Television footage and social media images showed police and residents transporting the injured to nearby hospitals.

Rescuers and the injured described a harrowing and chaotic scene, with bodies lying on the carpeted floor of the mosque.

Hussain Shah said he was praying in the mosque’s courtyard when a sudden, loud explosion occurred. “I immediately thought that some big attack has happened,” he told Associated Press.

When he entered the mosque, many of the injured were screaming and crying out for help. Shah said he counted about 30 bodies inside, while the number of injured appeared to be significantly higher.

Another person in a clip shared on social media said there were at least two attackers and that they had fired at people before detonating bombs. “People were lying in the pool of blood. I saw people’s heads and limbs separated from their bodies.”

Islamic State claimed responsibility for the attack on its Telegram channel. It has been blamed for previous attacks on Shia worshippers, who are a minority in the country. Militants often target security forces and civilians across Pakistan.

Though attacks are not so frequent in Islamabad, there has been a surge in militant violence in Pakistan in recent months, blamed largely on Baloch separatist groups and the Pakistani Taliban, known as Tehreek-e-Taliban Pakistan, which is separate from, but allied with, Afghanistan’s Taliban.

Pakistan’s president, Asif Ali Zardari, and the prime minister, Shehbaz Sharif, condemned the attack in separate statements and extended condolences to the families of those killed. They instructed that all possible medical assistance be provided for the injured.

“Targeting innocent civilians is a crime against humanity,” Zardari said. “The nation stands with the affected families in this difficult time.”

Sharif said he had ordered a full investigation. “Those who are responsible must be identified and punished,” he said.

Pakistan’s interior minister, Mohsin Naqvi, also condemned the attack, and asked authorities to ensure the best medical care was provided.

Friday’s attack occurred while Uzbekistan’s president, Shavkat Mirziyoyev, who is on an official two-day visit, was attending an event in Islamabad with Sharif. The event was several miles from the mosque.

A top Shia leader, Raja Nasir Abbas Jafri, expressed deep sorrow over the attack.

“Such a terrorist act in the federal capital is not only a serious failure in protecting human lives but also raises significant questions about the performance of the authorities and law enforcement agencies,” he said. He asked for people to donate blood as the hospitals in Islamabad were in urgent need of supplies.

Pakistan’s mainstream media faced a backlash after they initially failed to report the attack.

Nadir Gurmani, a journalist with Dawn TV, wrote on X: “Those who don’t understand why people are losing trust in traditional media should just look at the media’s role in today’s coverage of suicide blast in Islamabad. News was circulating on social media, but TV channels did not carry even a single ticker.”

One of the deadliest attacks in Islamabad took place in 2008, when a suicide bombing targeted the Marriott hotel, killing 63 people and injuring more than 250. In November last year, a suicide bomber struck outside a court in Islamabad, killing 12 people.

The latest attack comes nearly a week after the outlawed Balochistan Liberation Army carried out attacks in the south-western Balochistan province, killing about 50 people. Security forces killed more than 200 “terrorists” in response, according to the military.