KARACHI: A suspected suicide explosion targeting President Asif Ali Zardari's chief security officer killed at least three people in Karachi on Wednesday, police said.

Eleven others were injured in the powerful explosion which rocked the busy New Town neighbourhood in the heart of Karachi, less than a kilometre from the Quaid's mausoleum.

“Three people, including the president’s chief security officer, Bilal Sheikh, were killed in the bombing,” said Superintendent Police Usman Bajwa.

Pakistan's President Asif Ali Zardari said that "Bilal had rendered many sacrifices for the PPP and that he was not just a bodyguard but more like a son."

President Zardari also appealed to party workers to offer fateha for Bilal.

The president added that Bilal had accompanied Benazir Bhutto when she was attacked in Karachi on Oct 18, 2007.

Bilal Sheikh was an active worker of the Pakistan People’s Party, the ruling party in Sindh province.

A spokesman for the Bilawal House, President Zardari's private residence in Karachi, had earlier confirmed Sheikh’s death. Sheikh's driver was also killed in the explosion.

Bajwa said the attack appeared to be a suicide bombing. “Bilal Sheikh’s vehicle was the target of the attack,” he said.

Officials said the wounded included six police officers and one FIA personnel. The injured were shifted to a local hospital where a state of emergency was imposed.

Bilal Sheikh was said to be a trusted aide of President Asif Ali Zardari, had previously been in charge of Zardari's private residence in Karachi, and was also responsible for the security in Karachi of Bilawal Bhutto-Zardari, the president’s son and PPP co-chairman.

Sheikh had also been in charge of security for Zardari's wife, former prime minister Benazir Bhutto when she returned to Karachi from exile on October 18, 2007, two months before her assassination.

The explosion came on the eve of the holy Muslim month of Ramazan, due to be observed in Pakistan from Thursday.

Bajwa said Sheikh and his driver had gone to buy food for Ramazan, the fasting month, when his vehicle was targeted. "He had never taken this route before, and he always had security with him," he said.

Sheikh had survived two previous attempts on his life.

No militant group has claimed responsibility of the attack as yet, but the Tehrik-i-Taliban Pakistan have previously targeted the Pakistan People's Party for it's "secular views".

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

In a statement, Bilawal Bhutto-Zardari also condemned the attack, blaming an "anti-democratic and extremist mindset" to be behind the bombing. "We will not be intimidated by such cowardly acts and such acts will not deter our resolve to fight terrorism," he said.