Pakistan's parliament, dominated by President Pervez Musharraf's opponents, passed a resolution on Monday urging the government to seek a UN investigation of the killing of former prime minister Benazir Bhutto.
Bhutto was killed in a gun and bomb attack in the city of Rawalpindi on December 27 as she was coming out of an election rally. "(It) should probe and identify the culprits, perpetrators, organisers and financiers behind this heinous crime and bring them to justice," Law Minister Farooq Naek said of the investigation he wants set up.
Musharraf, who has become increasingly isolated after the crushing defeat of his allies in a February 18 election, has opposed a UN investigation of Bhutto's killing.
British police helped investigate the assassination and they backed up the government's explanation of how Bhutto was killed.
The previous government and the US CIA accused Baitullah Mehsud, an Al-Qaeda-linked militant commander based on the Afghan border, of killing Bhutto, a staunch supporter of the US-led campaign against Islamist militancy.
Mehsud's spokesman has denied involvement.
Bhutto's murder fuelled anger against Musharraf and many Pakistanis suspected that rogue elements in the intelligence agencies could have been behind the murder of the two-time prime minister and opponent of military rule.
Musharraf has denied his or his security agents' involvement in the killing. Bhutto's party, which now heads a coalition government, has demanded a UN investigation.
The National Assembly resolution, moved by Naek and unanimously adopted, urged the government to approach the United Nations with a view to forming an "international investigation commission".
Police have arrested at least four Islamist militants suspected of involvement in Bhutto's killing.
Bhutto's aides have expressed dissatisfaction over the investigations conducted by the authorities and there has also been a controversy over the cause of Bhutto's death.
British police, in their February findings, corroborated Pakistani investigators' findings that Bhutto was killed when the blast slammed her head against armour plating around the roof hatch in her vehicle, which she had stood through to wave to supporters. But her aides insist she was shot.