Scotland Yard sleuths on Friday began investigations into the assassination of former premier Benazir Bhutto, soon after their arrival from the United Kingdom, a day after President Pervez Musharraf [Images] said he was not fully satisfied with the probe.

The five-member team from the Metropolitan Police's Counter-Terrorism Command was briefed by Pakistani anti-terror experts on investigations conducted so far into her killing in a suicide attack last week.

However, Bhutto's Pakistan People's Party reiterated its demand for a probe by the United Nations, saying the Scotland Yard team could be made part of such an investigation.

The British team was briefed by officials of the Special Investigation Group, the anti-terror wing of Pakistan's Federal Investigation Agency, which is heading the ongoing investigation. Officials from Pakistan's interior ministry also met the team to discuss modalities for the probe.

A high-level meeting chaired by Musharraf, to review the law and order situation, also decided to extend complete cooperation to the British team.

Members of the British team refused to talk to reporters on their arrival at the international airport in Islamabad.

The team is expected to visit the site in Rawalpindi where Bhutto was attacked by a gunman and a suicide bomber, after addressing a rally, on December 27. It was not immediately clear how long the team would remain in Pakistan.

The PPP asserted that the UN alone could carry out an independent and impartial probe. PPP leader and Bhutto's lawyer Farooq Naek said: "We do not expect that any concrete material would be collected by this (British) team."

The Pakistan government has ruled out a probe by the UN on the lines of the world body's inquiry into the assassination of Lebanese premier Rafik Hariri, saying the circumstances in the two countries are different.

Naek said that the British team should have been brought in after the October 19 suicide attack on Bhutto's rally in Karachi that killed 140 people.

"But the government refused to bring in any foreign investigators then. Now, when the PPP has demanded a UN inquiry, we fail to understand why the government always creates obstacles, and doesn't listen to the aggrieved party," said Naek, who is part of a PPP panel of lawyers that is drafting a formal petition for a UN inquiry.

Naek said that the petition would be approved by PPP's co-chairman Asif Ali Zardari before being sent to the UN.

During an interaction with the international media on Thursday, Musharraf admitted that he was not fully satisfied with the investigations so far. He said the police should not have washed the site, where Bhutto was attacked, as this had destroyed forensic evidence. But he noted that this was done due to inefficiency and not by design.

He also indicated that the interior ministry should not have issued any definite statement about the cause of Bhutto's death. "One should not give a statement that's 100 per cent final. That's the flaw that we suffer from," he said.

Musharraf explained that his decision to seek Scotland Yard's help was aimed at addressing suspicions about the government's complicity in Bhutto's killing.

"Here's a situation where may be we need to go beyond ourselves to prove to the world and our people here, who are emotionally charged, that we don't mind going to any extent, as nobody is involved from the government side or the agencies," Musharraf said.

Bhutto's Pakistan People's Party has dismissed as lies the government's contention that she died of a skull fracture during the suicide attack and her close aides have said she was shot in the head.

This is the third time that British police expertise has been sought by Pakistan to investigate a high-profile political assassination in the country. But in the two earlier instances, the British teams were asked to leave Pakistan before they could complete their probe.

The first inquiry was conducted in the aftermath of the 1951 assassination of Pakistan's first prime minister Liaquat Ali Khan, who was ironically shot at the same site as Bhutto.

The British team was asked to leave Pakistan before its inquiries were complete and the case was closed.

A second British police team was sent to Karachi in 1996 to investigate the murder of Bhutto's estranged younger brother and political rival, Murtaza.

Bhutto was then the prime minister and her administration enlisted the services of Scotland Yard detectives and Home Office forensic experts.

Within six weeks of the killing, Bhutto's government was sacked for alleged corruption. The Scotland Yard team was then ordered to leave Pakistan with its investigation incomplete.