A mosque that was used mostly for police and security personnel was bombed on Monday, January 30, in Pakistan.

At least 100 people were killed, and hundreds more were injured in the blast, after a suicide bomber detonated a bomb inside the mosque.

The suicide bomber was able to enter through several security checks manned by officers to get into the “red zone,” an area that houses the country’s counter-terrorism and police offices in Peshawar, a volatile city in the northwest of Pakistan on the border of Afghanistan.

The mosque was crowded, with more than 300 men praying, and the explosion wounded about 225, with most in critical condition.

At least 100 people have died after succumbing to their wounds. Most were police personnel.

Sarbakaf Mohmand, a commander for the Pakistani Taliban, known as Tehreek-e-Taliban Pakistan  (TTP), and another member of the TTP, Mukaram Khorasani, initially claimed responsibility for the attack on Twitter. They said the attack was revenge for the killing in August 2022 of the group’s commander in Afghanistan.

A TTP spokesperson, Muhammad Khorasani, however, denied responsibility for the bombing. 

Investigations into how the attacker breached the secured area are underway, with officials investigating whether the bombing was an inside job or the bomber had help from someone on the inside.

The attack was the worst incident of terrorism in Peshawar since the March 2022 attack in a Shi’ite Muslim mosque by the Islamic State that left at least 58 people dead.

Peshawar borders Afghanistan, which the Taliban now controls. Militant groups, including the Pakistan Taliban and the Islamic State, have frequently targeted the city.

Videos shared on social media showed that half of the mosque’s wall was caved in, and the inside was covered in debris and bricks. People climbed over the ruins to escape.

The TTP has been launching attacks in Pakistan for over ten years, fighting for the government to enforce stricter Islamic laws and reduce military presence in the former tribal regions.

According to Pakistan Defense Minister Khawaja Asif, the suicide bomber was standing in the first row when the bomb went off.

An officer who survived the attack told reporters that as the prayer leader chanted “Allahu Akbar” or “Allah is Great,” the bomb went off.