At least nine policemen and a civilian were killed and 25 others injured in a massive explosion near the controversial Lal Masjid, minutes after thousands of Islamic hardliners demanded the public hanging of President Pervez Musharraf at a meeting to mark the shrine's storming by the Pakistani military.
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.
Musharraf, Aftab Sherpao (then interior minister) and others responsible for the bloodbath should be tried and hanged publicly," Islamist leader Idrees Haqqani said as the crowd raised their hands in approval chanted slogans like "God is great".
"A criminal case of mass murders should be registered against Musharraf and others responsible for the killings," another leader said.
TV channels reported that leaders of outlawed extremist groups like the Sipah-e-Sahaba and Jaish-e-Mohammed participated in the meeting.
Clerics said the conference was organised to pay respect to those who died when the army stormed the mosque in the heart of Islamabad after a siege in July last year.
Participants demanded the release of Lal Masjid cleric Abdul Aziz, the reopening of Jamia Faridia madrassa and rebuilding of Jamia Hafsa madrassa in line with an order issued by the Supreme Court.
Both the madrassas are affiliated to Lal Masjid. Jamia Faridia was closed after the military operation while Jamia Hafsa was razed. Abdul Aziz was arrested at the conclusion of the operation while his brother Abdul Rashid Ghazi was shot dead. Over 100 people were killed in the operation.
Hundreds of people, most of them seminary students, poured into Islamabad last night from all over Pakistan to participate in the conference.