A suicide bombing at a crowded mosque in Pakistan's Peshawar killed at least 32 people on Monday, the latest attack targeting police in this northwestern city where Islamist militants remain active.

Hospital officials said at least 147 people were wounded, with many of them in critical condition.

Prime Minister Shebaz Sharif called the blast a suicide attack. There were at least 260 people in the mosque, police official Sikandar Khan added.

No one has claimed responsibility for the bombing, which ripped through the mosque during noon prayers, causing a wall to collapse on top of worshippers. The building is located inside a highly fortified compound that includes the headquarters of the provincial police force and a counter-terrorism department.

"We're getting that the terrorist was standing in the first row," Defense Minister Khawaja Asif told Geo TV.

Footage from government broadcaster PTV showed police and residents scrambling to remove debris from the blast site and carrying wounded people on their shoulders.

The attack was the city's worst since March last year, when a suicide bombing at a Shi'ite Muslim mosque during Friday prayers killed at least 58 people and injured nearly 200. Islamic State militants claimed responsibility for that bombing.

Peshwar, which sits at the edge of Pakistan's tribal districts bordering Afghanistan, is frequently targeted by militant groups, including the Pakistani Taliban.

The group, known as Tehreek-e-Taliban Pakistan (TTP) is an umbrella of Sunni and sectarian Islamist groups that want to overthrow the government and replace it with their own brand of Islamic governance.

The TTP has stepped up attacks since it ended a so-called peace deal last year with the Pakistani government, which was facilitated by Afghan Taliban.

TTP has staged frequent attacks targeting police in the last few months. In December, Islamist militants seized a counter-terrorism centre in the northwestern and took hostages to negotiate with government authorities.