The city was at a standstill with shops and markets, government offices and educational institutions closed and public and private transport off the road.

At least 43 people were killed and 60 others injured when the bomber struck the procession on the M.A. Jinnah Road at about 4.15pm near the Light House area.

The plastic market in the Boulton Market area was ablaze till late in the night on Tuesday — about 40 hours after the tragedy —as fire brigade was unable to cope with a large number of fires raging along the M.A. Jinnah Road.

Monday's bombing came on the heels of two explosions of low intensity in the city on Saturday and Sunday in which no lives were lost.

The blast hit the front part of the procession which is considered to be most secure because it is guarded by heavy contingents of police and Rangers.

As Ashura mourners realised that a blast had taken place, a large number of them ran in frenzy towards the front looking for relatives and some mourners who were returning home rushed back to the area.

Cellphone networks stopped functioning for some time as families made frantic calls to their dear ones in the procession. “For a few seconds we went numb. Then ambulances started rushing towards the area to rescue the injured and retrieve bodies.

“A few minutes later police vans appeared on the scene and people in the procession vented their anger by pelting police with stones, forcing them to retreat,” Ali Mohsin, a witness, said. Gunshots were also heard amid the mayhem.

The injured were taken to the Civil Hospital, Jinnah Postgraduate Medical Centre and Aga Khan Hospital. Three scouts and a Rangers official also lost their lives.

A police officer who was at the site told Dawn that the explosion had taken place  between a police post and scouts' camps.

“The bomber apparently tried to step into the middle of the front part of the procession and the explosion took place at the extreme left side,” he said.

“No senior law-enforcement official was able to explain how the suicide bomber had managed to breach several security layers. Some mourners pointed out that the entry point near Subhanallah Bakery was being frequented by VIPs and media personnel and the bomber could have bypassed the security there.

The impact of the blast was so severe that a torso flew in the air and landed on the third floor of a building across the road. Some people left the procession after the explosion, but others stayed put and after reinforcement of security continued their march in a highly charged atmosphere towards Imambargah Husainia Iranian where a majlis of Sham-i-Ghariban was held.

The organisers persuaded security forces to provide cover so that the procession could reach its destination.

It later transpired that police investigators acted in haste and identified the remains of a victim as those of the suicide bomber. They also issued his picture to TV channels. After seeing the footage, the victim's family contacted the authorities and claimed the remains.

Investigators estimated that approximately 16kgs of explosives and nuts, bolts, and ball bearings had been used in the blast.

City police chief Waseem Ahmed said several bodies and eight limbs were still unclaimed. “We have carried out reconstructive surgery on the remains, but are waiting for claimants. If their heirs don't turn up we will go for DNA tests and fingerprinting to identify them.”

He said circumstantial evidence suggested that the bomber had used a suicide belt. An FIR was registered by Preedy police on behalf of the state.