Central Intelligence Agency (CIA) officials also agreed that Mehsud was the most likely culprit.

London's Scotland Yard was called in to determine whether Bhutto had died because of the gun shot wound or by hitting the sunroof of her vehicle. The British findings in favour of her having hit the sunroof were rejected by her party.

Bhutto's supporters, not satisfied by Pakistani investigations, have hinted that Musharraf and his allies were involved in the murder. When her husband Asif Ali Zardari became president, he asked the UN to carry out an independent investigation.

The commission will perform 'fact finding activities in Pakistan and abroad', according to the office of the secretary general.

Its final report will be presented to UN chief Ban Ki-moon within six months. The findings will be shared with the Pakistani government and the Security Council 'for information'.

Several observers have criticised the commission for having a weak mandate as compared to the UN probe into the 2005 killing of former Lebanese prime minister Rafik al-Hariri, which also provides for a court to try the perpetrators at The Hague.

(Betwa Sharma can be contacted at betwasharma@gmail.com)