KARACHI, PAKISTAN, OCT. 10 -- Asif Ali Zardari, husband of former Pakistan prime minister Benazir Bhutto, was arrested here today on charges of kidnapping, extortion and loan fraud.

Senior government officials said Zardari would be charged in three separate cases. The most serious involves charges that Zardari participated in the kidnapping and robbery of a London-based businessman.

The charges by Pakistan's caretaker government come as Bhutto, who was dismissed from office in August, is attempting to mount a campaign to regain power in elections Oct. 24.

Bhutto, who faces trial on corruption charges, denied the allegations against her husband at a press conference here today and said that Zardari's arrest was "an attempt by the government to blackmail" her Pakistan People's Party.

Officials said Zardari's arrest stems from the alleged September 1989 kidnapping of Murtaza Hussain Bukhari, 55, a British citizen of Pakistani descent. Bukhari has alleged in police statements and interviews that after coming to Karachi to build a hospital for the mentally handicapped, he was abducted, beaten and forced to turn over about $500,000 in rupees to his kidnappers.

Karachi police filed charges in the case earlier this year against four men, including Ghulam Unar, a People's Party provincial legislator and mayor of Benazir Bhutto's home town. Unar was arrested, but Bhutto refused to unseat him from his offices, saying in interviews that the case had been fabricated in a conspiracy against her government.

Police apparently stepped up their investigation after Bhutto's government was dismissed on Aug. 6 by President Ghulam Ishaq Khan in a move backed by the military.

In statements to Pakistani police, British authorities, and the press, Bukhari has said that he met with Zardari and Unar prior to his kidnapping and that Zardari vouched for Unar's integrity, urging Bukhari to turn over funds to the mayor for construction of the hospital. Bukhari said that several days later, Unar and three others kidnapped him, beat him, tied what he believed was a bomb to his leg, and forced him to withdraw money from his London accounts.

Bukhari said in an interview that during his detention, his kidnappers told him that Zardari was to receive part of the ransom.

Police officials said they arrested Zardari today because they have obtained statements from three participants in the kidnapping that Zardari did indeed receive some of the stolen funds. The police officials also said they had bank records and other documentary evidence.