Pakistani residents gather after the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Pakistani rescuers evacuate a victim from the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. RIZWAN TABASSUM/AFP/Getty Images
A Pakistani rescuer carries an injured man at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. RIZWAN TABASSUM/AFP/Getty Images
People gather as firefighters try to extinguish fire at the site of bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Residents stand in front of a damaged building after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Akhtar Soomro
Firefighters spray water to control a fire in a building after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Akhtar Soomro
Residents stand in front of a damaged building after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Akhtar Soomro
Pakistani rescuers gather at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Pakistani rescuers gather at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Residents and firefighters gather at the site after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Akhtar Soomro
Pakistani rescuers work at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
A Pakistani rescuer works at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Pakistani medics and civilians gather at the site of a bomb blast in Karachi, Pakistan, Sunday, March 3, 2013. Pakistani officials say a bomb blast has killed dozens of people in a neighborhood dominated by Shiite Muslims in the southern city of Karachi. (AP Photo/Fareed Khan)
Pakistani medics and civilians gather at the site of a bomb blast in Karachi, Pakistan, Sunday, March 3, 2013. Pakistani officials say a bomb blast has killed dozens of people in a neighborhood dominated by Shiite Muslims in the southern city of Karachi. (AP Photo/Fareed Khan)
Pakistani rescuers search for victims at the site of the bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. ASIF HASSAN/AFP/Getty Images
Residents search for their belongings after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Akhtar Soomro
Pakistani children, who were slightly injured in a bomb blast, are brought to a hospital in Karachi, Pakistan, Sunday, March 3, 2013. Pakistani officials say a bomb blast has killed dozens of people in a neighborhood dominated by Shiite Muslims in the southern city of Karachi. (AP Photo/Shakil Adil)
Rescuers evacuate an injured bomb blast victim after an explosion damaged two residential buildings in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. RIZWAN TABASSUM/AFP/Getty Images
Rescue workers and residents gather at the morgue to identify relatives after a bomb blast in a residential area in Karachi March 3, 2013. A bomb attack in a Shi'ite Muslim area of Pakistan's commercial capital Karachi killed 25 people and wounded 50 on Sunday, the police said. REUTERS/Athar Hussain
A Pakistani man, who lost a relative in a bomb blast, reacts at a hospital's morgue in Karachi, Pakistan, Sunday, March 3, 2013. Pakistani officials say a bomb blast has killed dozens of people in a neighborhood dominated by Shiite Muslims in the southern city of Karachi. (AP Photo/Fareed Khan)
A Pakistani man, reacts next to the body of a relative who was killed in a bomb blast, at a hospital's morgue in Karachi, Pakistan, Sunday, March 3, 2013. Pakistani officials say a bomb blast has killed dozens of people in a neighborhood dominated by Shiite Muslims in the southern city of Karachi. (AP Photo/Fareed Khan)