The powerful blast, which was heard from several kilometres away, occurred as a large crowd of slogan shouting and flag waving people, including madrassa students and outlawed extremist groups like the Sipah-e-Sahaba and Jaish-e-Mohammed, began dispersing at about 7.50 PM.

Witnesses said the explosion occurred in the vicinity of a petrol station near Melody Market, which is located adjacent to the Lal Masjid and created panic among the people who ran back towards the mosque.

Body parts and pools of blood lay strewn all over the area, which was cordoned off by the police. Nine of the dead were policemen.

A high alert was declared in Islamabad while an emergency was declared in all the hospitals of the capital.

The blast targeted the site where a large number of policemen had gathered as part of the security arrangements for the meeting where several clerics made hard hitting speeches criticising the arrest of former Lal Masjid cleric Maulana Abdul Aziz as well as the government's plans for reforming madrassas.