ISLAMABAD - Pakistan has asked the United Nations to investigate the assassination of former prime minister Benazir Bhutto.

Foreign Ministry spokesman Mohammed Sadiq says Pakistan's ambassador to the UN handed the request to the world body's secretary general, Ban Ki-moon, in New York on Friday.

It's unclear when Ban will make a decision and whether he will refer the matter to the UN Security Council.

Bhutto died in a gun-and-suicide bomb attack on Dec. 27 as she left an election rally in the city of Rawalpindi.

Her death shocked the world and Pakistan, fanning revulsion at rising militant violence as well as conspiracy theories that Pakistan's powerful spy agencies were involved.

It also helped carry her Pakistan People's Party to victory in February elections.

The party leads a seven-week-old coalition government that has made a UN probe into who was behind the killing a top priority.

The previous government and the CIA quickly accused Baitullah Mehsud, a Pakistani militant commander often blamed for suicide attacks, of orchestrating the killing.

Pakistan's Interior Ministry released a wiretap in which Mehsud associates purportedly congratulated each other for her death. Bhutto had called for Pakistan to redouble its efforts against Islamic extremism.

President Pervez Musharraf and the United States have opposed a UN investigation.

But Bhutto's party argues that the world body should probe the killing given Mehsud's alleged links to al-Qaida and because of the huge political controversy that surrounds the case in Pakistan.

Sadiq said Foreign Minister Shah Mehmood Qureshi would soon travel to New York for talks with Ban and members of the Security Council. He said he was confident the UN would accept the request.

A UN spokeswoman said last month that Ban was likely to refer the matter to the Security Council.