Benazir Bhutto's party plans to launch a vigorous campaign for Pakistan's Feb. 18 parliamentary election once the 40-day mourning period for the slain opposition leader ends this week, her supporters said Sunday.

Campaigning for the crucial election all but ceased after Bhutto was killed in a Dec. 27 suicide attack during a rally in the northern city of Rawalpindi, promoting authorities to postpone the balloting for six weeks.

U.S. and Pakistani officials blamed the assassination on Pakistani militants with links to al-Qaida, and the government repeatedly urged parties to avoid big public rallies because the extremists were believed to be planning more attacks.

Underscoring the threat, a suicide bomber Monday rammed his motorbike into a minibus carrying security personnel in Rawalpindi, detonating an explosion that killed at least six people, police said.

Despite the warnings, officials of Bhutto's Pakistan Peoples Party said her husband, Asif Ali Zardari, would lead a series of "mammoth rallies" after the mourning period ends Thursday.

Another major opposition party, the Pakistan Muslim League-N of former Prime Minister Nawaz Sharif, was also expected to step up the tempo with just two weeks left before the vote. Sharif's party also slowed its campaign after Bhutto's death.

Sharif returned from exile in November to lead a campaign against President Pervez Musharraf, who ousted him in a military coup eight years ago.

The United States and other Western nations hope the elections will help bring stability to this nuclear-armed country as it battles rising attacks by al-Qaida and Taliban militants. The violence is undermining public support for Musharraf, who gave up his post as head of the army last year in an effort to stifle calls for him to step down.

Despite the short time remaining before the balloting, Babar Awan, a senior member of Bhutto's party, said the opposition will reach out to voters across the country in a series of rallies expected to begin late this week in Sindh province, her party's stronghold.

Awan said Peoples Party candidates have been running low-key campaigns in their home constituencies during the mourning period, but he hoped public appearances by Zardari would help rally nationwide support.

He demanded that the government provide security for Zardari and other candidates.

Some opposition leaders have accused the government and intelligence agencies of complicity in the Dec. 27 attack against Bhutto.

Bhutto's followers have accused Musharraf's government of failing to protect the former prime minister, who escaped assassination in October when a suicide bomber attacked her motorcade in Pakistan's largest city, Karachi, shortly after she returned from more than seven years in self-imposed exile.

The spokesman for Pakistan's Interior Ministry, Javed Iqbal Cheema, said all police and security agencies had been ordered to provide protection for Zardari and all other candidates.

Sadiq ul-Farooq, a senior member of Sharif's party, claimed other opposition figures were being targeted for assassination to disrupt the election and "perpetuate the tyrannical rule of Musharraf."

"If the elections are not rigged, we will definitely win," he told The Associated Press.

But Awan said Bhutto's death had generated such sympathy for her party that "there is no doubt we will win the elections with a majority and form a new government."

Parliament re-elected Musharraf in October but needs a two-thirds majority in the 342-member body to stave off any bid for his impeachment. The embattled president has given assurances that the elections will be "free, fair and transparent."

In an editorial Sunday, the English-language newspaper The News called on Musharraf to step down after the new parliament is elected and "preside over the transition in a dignified and respectable manner."

Bhutto herself wrote in an autobiography to be published next week that she had been warned that four suicide bomber squads, one led by Osama bin Laden's 16-year-old son Hamza, would try to kill her.

She wrote that Musharraf and a "foreign Muslim government" had informed her these squads were planning her murder.

Excerpts of the book, first published by The Sunday Times of London, were confirmed by The Associated Press, which obtained an uncorrected proof of the book. The book is to be published on Feb. 12.