Saboteurs have blown up part of a key oil pipeline in northern Iraq, while clashes left four Iraqis dead and three US soldiers lightly wounded as yet another tape purporting to be from Saddam Hussein popped up on Arab television Friday.

Polish troops joining the US-led coalition's rebuilding efforts also received their baptism of fire when five mortar bombs were launched at their base in Hilla, south of Baghdad, with the violence coming three months to the day since US President George W. Bush declared the war effectively over.

The pipeline fire in the northern refinery hub of Baiji, still seen raging in northern Iraq Friday, was certain to throw off US plans to further resuscitate Iraq's massive but crippled energy sector.

Only a day earlier, US officials hailed the expected reopening early this month of the country's main oil pipeline from the petroleum centre of Kirkuk to
the Turkish Mediterranean terminal of Ceyhan, wrecked in a previous sabotage attack.

Oil exports are supposed to provide the financial muscle needed to foot the massive bill for Iraqi reconstruction expected to run to tens of billions of
dollars per year.

In other acts of defiance, suspected former regime loyalists in the Fallujah area again clashed with US troops Friday amid an escalation of anti-US violence in the region west of Baghdad seen as a haven of Saddam supporters.

Four Iraqi men were killed when they assaulted a US military convoy with rocket-propelled grenades (RPGs), Sergeant Keith O'Donnell said at a US base in Ramadi, a flashpoint town near Fallujah where US troops come under daily attack.

The military arrested nine Iraqis and confiscated several RPGs as well as documents bearing photographs of Saddam.

"It was one of eight attacks in the last 24 hours west of Baghdad, the most extensive attacks in a while," Sergeant O'Donnell said.

He also said, in a separate incident, three soldiers were lightly wounded when their vehicle was struck by an improvised explosive device near a US base.

As the assaults on US forces continued unabated, so did the hunt for Iraq's most-wanted man, with optimism that the ousted strongman will be found growing
since the death of his two sons July 22.

The United States wants a special panel of Iraqi judges to try the toppled dictator for crimes against humanity if he is captured alive, The New York Times said.

"The Iraqis will play the undisputed leadership role in this process," a senior State Department official told the newspaper, but Iraqi judges on the court would be free to solicit outside help in the trials.

Finding Saddam is clearly a top priority for the United States, which has handed out retouched photographs showing the ousted strongman without a
moustache, with a beard and in other possible guises.

The photos were the latest indication of an increasingly concentrated search for Saddam, who US intelligence sources assume has tried to change his
appearance to escape capture after four months on the run.

The elusive former president has purportedly delivered a new message to the Iraqi people, with a voice said to be his popping up on Qatar's Al-Jazeera
satellite TV Friday.