Peshawar (Pakistan): Distraught relatives thronged hospitals in Pakistan's Peshawar on Tuesday to look for their kin a day after a suicide bombing ripped through a crowded mosque in a heavily fortified area of the city, killing 100 people, mostly policemen.

The attack, in the Police Lines district, was the deadliest in a decade to hit this restive, northwestern city near the Afghan border and comes amid a surge in violence against the police. No group has claimed responsibility.

"My son, my child," cried an elderly woman walking alongside an ambulance carrying coffins, as rescue workers stretchered wounded people to a hospital emergency unit.

At least 170 people were wounded in the blast, which demolished the upper storey of the mosque as hundreds of worshippers performed noon prayers.

Riaz Mahsud, a senior local government official, said the casualty toll was likely to rise as workers searched through the debris just over 24 hours later.

"So far, 100 bodies have been brought to Lady Reading Hospital," the spokesman for the largest medical facility in the city, Mohammad Asim, said in a statement.

Authorities say they do not know how the bomber managed to breach the military and police checkpoints leading into the Police Lines district, a colonial-era, self-contained encampment in the city centre that is home to middle- and lower-ranking police personnel and their families.

Given the security concerns in Peshawar, the mosque was recently built to allow police to pray without leaving the area. Defence minister Khawaja Asif said the bomber was in the first row in the prayer hall when he struck.

The attack is the deadliest in Peshawar since twin suicide bombings at All Saints Church killed scores of worshippers in September 2013, in what is the deadliest attack on Pakistan's Christian minority.

Peshawar sits on the edge of the Pashtun tribal lands, a region mired in violence for the past two decades. The most active militant group in the area is the Pakistani Taliban, also called Tehreek-e-Taliban Pakistan (TTP), an umbrella group for Sunni and sectarian Islamist factions opposed to the government in Islamabad.

The TTP denied responsibility for Monday's bombing, though it has stepped up attacks since withdrawing from a peace deal with the government last year.

The bombing took place a day before an International Monetary Fund (IMF) mission arrives in Islamabad for talks on a stalled $7 billion bailout.