Many of his criticisms have been aimed particularly at Prime Minister Bhutto, who Mr. Khan has accused of leading a Government obsessed with political vendettas and self-enrichment. Ms. Bhutto has responded by targeting Mr. Khan with income tax investigations, a ban on fund-raising events for the cancer hospital in schools and other Government-run institutions, and a blackout on reports about the hospital on the state-run broadcasting network.

After the explosion today, the 42-year-old Ms. Bhutto made her first visit to the hospital, calling the blast "a deplorable attack" and hinting that it might have been the work of loyalists of Pakistan's main opposition leader, Nawaz Sharif. Mr. Sharif, who has tried and failed to recruit Mr. Khan as an ally, denied the allegation.

Mr. Khan, who reached the hospital from his home in Lahore shortly after the attack, declined to say who he thought might have set the bomb. But he said the blast would not deter him from his political plans. "I want to tell those who want to scare me that neither will I be scared, nor will I turn back," he said. "I will move forward with greater determination."

Mr. Khan has stirred controversy in Pakistan for what his critics call hypocrisy. He has described the country's political elite as "brown Sahibs" -- meaning that their attitudes and life styles, in a Muslim country, mimicked those of the British rulers of colonial India. Opponents responded that Mr. Khan, during his cricket career, was one of the most photographed "playboys" of London's West End.

Last summer, Mr. Khan stunned many Pakistanis by marrying Jemima Goldsmith, now 22, who is the daughter of James Goldsmith, an Anglo-French business tycoon. After Muslim ceremonies in Paris and a civil wedding in London, Mrs. Khan, who adopted the Muslim name Haiqa and converted to Islam, made a home with Mr. Khan in Lahore.