Operation Ivy Lightning, launched on Monday, was the latest effort by the US 4th Infantry Division to hunt down pro-Saddam guerrillas blamed for a wave of attacks that has killed 56 American soldiers since the start of May.

The operation focused on remote villages around 80 miles north of Baghdad, after intelligence reports suggested Saddam loyalists may have fled there to escape repeated raids around the deposed president's hometown of Tikrit.

Lieutenant Colonel William MacDonald of the 4th Infantry Division told reporters at his headquarters in one of Saddam's lavish former palaces in Tikrit that progress was being made in rounding up guerrillas and lower-level Saddam loyalists.

"We're not so focused on one individual," he said.

"We're more resolved to go after mid-level leaders and foot soldiers because they are the ones recruiting and organizing subversive activity against us."

US officers said that of several people detained during Operation Ivy Lightning, all but two had been released.

Saddam remains on the run despite an intense US manhunt and a US$25 million price on his head. His feared sons Uday and Qusay were killed last month in an American raid on their hideout in the northern city of Mosul.

US officers in Tikrit said that in separate raids over the past day, 14 Saddam loyalists had been detained in the restive region north of Baghdad.

Anger Smolders in South

Violence against occupying troops has mainly been concentrated in Baghdad and in the Sunni Muslim areas of central and northern Iraq where support for Saddam is still widespread. But chronic shortages of power and fuel also sparked unrest in the Shi'ite south over the weekend.

At least two Iraqis and a Nepalese security guard were killed on Sunday in violence in the city of Basra, after locals enraged by a lack of electricity and petrol confronted British troops, threw rocks and blocked roads with burning tires.

Unrest also affected the town of Safwan on the border with Kuwait. Kuwaiti authorities closed the border crossing for several hours on Sunday and again on Monday after cars and trucks belonging to Kuwaitis were attacked by locals in Safwan.

British troops have been distributing petrol to gas stations in an effort to calm tensions in the region, but many locals remain angry that fuel is being rationed.

The US-led administration blames the energy crisis in southern Iraq on sabotage of power lines and pipelines, rampant smuggling of oil products and the breakdown of decrepit equipment in power stations and refineries.

The main oil refinery in southern Iraq was forced to shut down on Sunday due to lack of electricity. But the ramshackle plant was started up again on Monday afternoon, the director of its engineering unit said.

"Yesterday after 2 p.m. (6 a.m. EDT) the electricity returned. We began the start-up of the refinery process about an hour after that," said Jamal Samman at the refinery, which has a capacity of about 140,000 barrels per day.

"But we are still only in the early stages of start-up."

The problems in southern Iraq have dealt another blow to Iraq's ability to produce and export oil -- a key prerequisite for economic recovery in the war-scarred country.