Brigadier Javed Cheema, an interior ministry spokesman, said on Saturday: "Security has been tightened and a joint investigation team has been assembled."
 
Cheema said the suicide bomber's remains were being DNA tested.
 
The man had explosives strapped to his body and was in a row of Punjab police when he detonated his load.
 
One witness, Nisar Ahmed, said: "It was a very big blast. I myself saw two bodies flying into air and falling on the road."
 
Protest

Earlier Pakistani police had fired tear gas to disperse protesting radical religious students who had spoiled government plans for the resumption of religious activities at the mosque complex, which had been a battleground earlier this month.

The students occupied the Red Mosque demanding the return of its pro-Taliban imam.
 
The students prevented the government-appointed imam from leading Friday communal prayers.
 
Hundreds of protesters threw stones at an armoured personnel carrier and dozens of police in riot gear on a road outside the mosque.

Paint job

 Pakistani police fired tear gas at
Islamist protesters throwing stones [AFP]
The group chanted slogans against Pervez Musharraf, the president, and called for Ghadi Abdul Aziz to be released.

The mosque had been hastily restored and reopened after it was damaged in fighting between students at the neighbouring religious college and government troops.

Its roof has been replaced, and bullet-scarred walls patched and painted in yellow. The rooftop minarets have been recoated in white.

Kamal Hyder, Al Jazeera's correspondent in Islamabad, said students arrived at the mosque armed with red paint and quickly began repainting the mosque its original colour.

The study centre was also badly damaged in the assault and has since been demolished.

Workers had pitched tents on Thursday in anticipation of worshippers filling the main hall on Friday and spilling over outside into Islamabad's monsoon-season heat and humidity.

Outside the mosque, dozens of police and paramilitary officers remained on patrol, and barbed wire still encircled part of the complex.

Police storm

The mosque was left scorched by explosions and sprayed with bullets after commandos stormed the complex on July 10 to end a week-long siege by those inside. At least 102 people died in the fighting and violence earlier in the siege.

The Red Mosque was riddled with bullets [AFP]

Ul-Haq said that 50 bodies found in the mosque after the siege were still to be identified.

He denied that the government was hiding the exact number of casualties. 

After the siege, the government sealed off the central mosque and moved quickly to have it repaired, amid outrage in Pakistan that a sacred place had been the scene of violence.

Ul-Haq said the government will pay for the education and accommodation of students from the demolished study centre if asked for.

A senior municipal official said the school would not be reconstructed.