A suicide bomb blast ripped through a crowded anti-government rally in central Islamabad, just minutes before the country's suspended chief justice was set to appear.  From Islamabad, VOA Correspondent Benjamin Sand reports at least 16 people were killed and many others seriously injured.

Ambulances and emergency personnel rush in to help clear the dead and carry the wounded to nearby hospitals.

Blood, body parts, and broken glass lay scattered on the street.

Witnesses say a lone suicide bomber approached a small stall built by the opposition Pakistan Peoples Party.

Ayaz Ali Khan says the bomb ripped through a group of protesters, sending bodies flying high into the air.

"Many peoples were crying they were injured, and most of them were saying, 'Help us', and 'Pick us up', and there was no ambulance, nothing, then after I think 10 minutes the ambulances came," he said.

This was Pakistan's fifth suicide bombing in as many days, but the first in the capital.

Security throughout the country has been stepped up since government commandos stormed a pro-Taleban mosque in Islamabad.  At least 75 people were killed in the bloody siege and militant forces are vowing revenge.

It remains unclear if Tuesday's attack is directly connected to the controversial siege.  The bomb detonated just outside a court where suspended Chief Justice Iftikhar Chaudhry was scheduled to speak.

The judge helped galvanize anti-government sentiment after Pakistan President Pervez Musharraf suspended him March 9.

Witnesses say the bomber was apparently targeting Chaudhry's supporters.

Opposition lawmaker Iqbal Zafar Jhagra witnessed the bomb attack and says there is only one person to blame.

"I do not know who did this, but I the only one person who is responsible, his name is General Musharraf," he said.  "Because of his policies, innocent persons have been killed."

Officials say they have launched a full-scale investigation in to the incident.

Whatever the motive, witnesses say the attack is surely adds to the growing sense of crisis in the capital and around the country.