With all Iraq?s oil exports halted by sabotage, gunmen killed a top Iraqi oil official yesterday in a new blow to an interim government reeling from violence two weeks before US-led occupation formally ends.

The shadowy guerrillas who have choked Iraq?s oil lifeline have also intensified a campaign of assassinations and suicide bombings intended to prove that the new Iraqi government cannot hope to assert control after the June 30 handover.

A car bomb attack destroyed an Iraqi police car and a civilian vehicle carrying foreigners in the western city of Ramadi yesterday, killing at least four Iraqis.

Witnesses said several foreigners were also believed to be among the casualties. Jabar Humadi, a doctor at Ramadi?s main hospital, said four bodies had been brought in after the blast.

Gunmen killed Ghazi Talabani, 70, a senior adviser in Iraq?s North Oil Company, in the northern city of Kirkuk, in the latest of many attacks on Iraqis accused by insurgents as collaborating with the US-British occupation.

Police said Talabani was shot as he was being driven to work. His driver was badly wounded. The gunmen escaped.

Manna al-Ubeidi, a senior official of the company, said Talabani, a second cousin of Kurdish leader Jalal Talabani, was a popular figure who had refused to employ bodyguards.

An Iraqi official said all crude oil exports from southern Gulf ports had stopped after saboteurs hit pipelines feeding the Basra and Khor al-Amaya terminals this week. Sabotage had already stopped exports via a northern pipeline to Turkey.

Iraq was exporting over 1.6 million barrels per day (bpd) of oil, its only independent source of revenue, and had hoped to match prewar levels of some two million bpd by June 30. Before the 1991 Gulf War, exports ran at just over three million bpd.

Industry sources said repairs could take at least a week, costing Iraq nearly $60 million a day until deliveries resume.

Saddam transfer

Guerrillas are believed to include former Saddam loyalists, nationalists from the minority Sunni Muslim sect to which the former president belongs, and foreign Islamic militants, some of them linked to al Qaeda ? and all opposed to the occupation.

As attacks surged elsewhere in Iraq, a radical cleric from the majority Shi?ite sect in the sacred city of Najaf told his Mehdi Army militiamen to go home, possibly signalling the end of his two-month-old uprising against US-led forces.

Moqtada al-Sadr issued a statement ordering fighters who are not from Najaf to return home to ?do their duty?.

Sadr agreed to a truce this month after weeks of fighting with US-led forces in Najaf and Kerbala. He was under pressure from senior Shi?ite clerics opposed to the violence and shocked at damage to Shi?ite Islam?s holiest shrines.

The cleric said this week he would set up a political party, which could contest national elections to be held by January. Iraq?s interim president has welcomed that idea.

Sadr?s forces have been keeping a low profile in Najaf since the truce, under which US forces also agreed to pull back from the town and turn security over to Iraqi police.

The approaching handover to the interim government has sharpened debate over the fate of Saddam Hussein and thousands of other Iraqis held by US-led forces in Iraq.

US President George W. Bush said on Tuesday he would not hand over the deposed dictator to the interim government until it has secure facilities to ensure he does not escape trial.

The Bush administration was prepared to transfer ?legal custody? of Saddam to the new government, but the US military would continue to hold him physically, officials said.

It would not promise to hand over Saddam or other prisoners by June 30, as asserted by interim Prime Minister Iyad Allawi.

The White House said a UN Security Council resolution passed last week gave US forces the authority to hold prisoners deemed to be security threats after June 30.

A State Department spokesman said international law allowed prisoners of war to be detained ?as long as the hostilities continue ... it is quite clear at this point that hostilities continue?.

Top US commander replaced

Human rights groups say that if the occupation ends, that would end international conflict in Iraq. All prisoners of war should then be freed, along with other detainees, unless there are grounds under Iraqi law, consistent with international human rights law, to continue their detention.

US troops captured Saddam in December. He has been in US custody as a prisoner of war at an unknown location.

Washington has agreed to give him and other officials in US hands to the Iraqis for trial once a sovereign government sets up a tribunal able to conduct a fair trial after June 30.

The Pentagon said General George Casey, the army?s second most senior officer, had been nominated to become the top US commander in Iraq, replacing Lieutenant General Ricardo Sanchez, who is under scrutiny over a prisoner abuse scandal.

Two Iraqis were killed on Tuesday when gunmen attacked a convoy carrying members of US security firm DynCorp near Baghdad international airport, the US military said.

One of the victims was a Dyncorp employee, the other a passerby caught in crossfire when people in the convoy returned fired at their attackers, a US spokesman said yesterday.

Alistair LYON