A suicide bombing at a Shiite mosque in Pakistan's capital Islamabad killed at least 31 people on Friday, local authorities said, with a police source saying more than 130 were wounded.

City officials said "31 people were killed in the blast" at the Imam Bargah Qasr-e-Khadijatul Kubra mosque in the Tarlai area on the outskirts of Islamabad.

A senior police official told AFP, on condition of anonymity, that the explosion occurred after Friday prayers, when mosques around the country are packed with worshippers.

The casualty toll was "expected to rise further", he added.

A security source also told AFP: "The attacker was stopped at the gate and detonated himself."

Yellow crime scene tape surrounded an investigation area, with shoes, clothing and broken glass scattered around the site.

Pakistan's Prime Minister Shehbaz Sharif condemned the blast, saying those behind it would be found and brought to justice.

Deputy Prime Minister Ishaq Dar branded the attack "a heinous crime against humanity and a blatant violation of Islamic principles".

"Pakistan stands united against terrorism in all its forms," he added in a post on X.

No group immediately claimed responsibility for the attack, which comes as Pakistan's security forces battle intensifying insurgencies in both the southern and northern provinces of the country that border Afghanistan.

The last major attack in Islamabad took place in November when a suicide blast outside a court killed 12 people and wounded dozens, the first such incident to hit the capital in nearly three years. (AFP)