Karachi Terrorists Bomb the Wounded at a Hospital

Militants bombed a hospital filled with the casualties of an earlier attack in Karachi today, killing more than 20, injuring at least 80 and setting Pakistan's largest city and economic hub on edge.

The first attack targeted a bus filled with mostly with women and children on their way to a religious festival. A second bomb exploded just outside the emergency room of Jinnah Hospital where the wounded were being treated and where their families had gathered to check on their status.

A third bomb was defused at the scene, police told reporters.

VIDEO: Attackers detonate a bomb at a hospital in Karachi. (No Audio)Play

"When the blast went off outside, then it was all darkness," Seemi Jamali told Reuters outside the hospital. "There was absolute chaos and people ran out of hospital from whichever door they could access."

The coastal city was already on edge from sectarian and political violence over the last few weeks, and residents and city officials said they expected rioting to follow today's attacks.

The attacks against minority Shiites will have a destabilizing effect on all of Karachi and on the rest of the country. Attacks in Karachi tend to force the city to shut down along with the stock market and most foreign and domestic investment, helping to choke the country financially.

"My city's potential is a threat to our enemies," Karachi Mayor Mustafa Kamal told ABC News. "Anyone who wants to destabilize Pakistan would try to destabilize Karachi and its economic engine."

The first bomb, which police said was driven into the bus by a bomber on a a motorcycle, exploded at about 3:15 p.m. local time, killing at least 12 Shiite mourners driving toward a procession in downtown Karachi.

The victims were marking Chehlum (known as Arbaeen in Arabic speaking countries), the end of a period when Shiites commemorate the slaying of Imam Hussein, the prophet's grandson. Forty days ago on Ashurra, the most important date on the Shiite calendar, militants also attacked Shiite mourners in Karachi, killing more than 40 people.

"A motorcyclist exploded near a bus ahead of us. We took off and rescued wounded," a witness told the Associated Press, declining to give his name. "It's cruel. They are not Muslims. They are not human. The government is responsible because it has failed to provide us security and control terrorists."

The second attack occurred just before 5 p.m. in the middle of a crowd of ambulances parked outside the emergency room where casualties of the first attack were being treated. Among the wounded were family members, journalists who had rushed to the scene, and emergency workers. A hospital official said as many as 10 people there were killed.

In CCTV video released by the hospital to the Pakistani TV channel GEO, hundreds of people are seen running from the explosion, their faces filled with fear and terror.

In the last week violence between sects and political parties in Karachi have killed about 40 people, leading the municipal government to hand over the city's security to the Rangers, an elite paramilitary force that was patrolling Karachi's streets today.

When reached by phone, the mayor admitted he no longer had a direct line to the security forces, saying they were operating entirely independently from the city's government.

Before the attacks today, Rangers had created cordons of security around the Shiite mourners who marched through the city. That march continued without incident, even after the bus bomb a few miles away.

Next to the scene of the bus attack, Ashfaq Ali sat near a pool of blood. He survived the attack. His two sons did not. "I will keep sitting here because it is my sons' blood," he told the Associated Press. "I want the terrorists to kill me as well."