At least four people, including the chief security officer of Pakistani President Asif Ali Zardari, were killed and 12 others injured on Wednesday when a powerful blast targeted a bullet-proof vehicle in a congested area in Karachi.

Bilal Sheikh, CEO of President Zardari in Karachi and a prominent leader of the Pakistan Peoples Party (PPP), was killed when the bomb ripped through his double cabin car in Gurumandir area, one of the city’s busiest locations.

A presidential spokesman said that Mr. Zardari is in Karachi but he was nowhere near the attack and was completely safe.

Rescue teams have shifted the four dead and 12 injured people to hospitals, rescue official Anwar Kazmi said.

Chaudhary Aslam, a senior police official, confirmed that Mr. Sheikh had been killed in the bomb attack.

Mr. Aslam said that the remote controlled bomb was planted in the double cabin car and was detonated when the car was at Gurumandir, where it stopped for a while.

Usman Bajwa, another police official, told the media that the bullet proof car was not properly built as it failed to sustain the impact of the bombing.

An official of the bomb disposal squad told Geo TV that four kg of explosives were used in the attack.

Nobody immediately took the responsibility of the attack.

Mr. Zardari and Prime Minister Nawaz Sharif “strongly condemned” the attack, state media said.

Mr. Sheikh, a die-hard leader of the PPP was party president of the central district in Karachi.

“He had received several threats and a cracker bomb attack was also carried out against him in Nazimabad two months back. He was transferred from the Presidency to Karachi”, an officer said.

Television channels gave conflicting reports that the bomb was planted on the roadside and was detonated when the car passed it.

An eyewitness said that besides those in the car several other bystanders were injured by the blast. Some vehicles which were close were also damaged.

“It was a powerful explosion and it caused plenty of damage and also spread panic and fear in the area with shops closing down immediately afterwards”, a rescue official said.