The besieged central Iraqi city of Fallujah was the scene of new explosions and gunfire Wednesday afternoon following an evening of U.S. warplanes targeting insurgent positions.

Network pool video Wednesday showed smoke rising from the direction of a train station and U.S. Marine helicopters hovering overhead.

The sound of gunfire could be heard coming from the area as U.S. choppers fired missiles at insurgent targets in the city west of Baghdad.

On Tuesday night, two AC-130 gunships fired 105 mm cannons at two suspected insurgent positions in Fallujah, military officials said.

Columns of smoke rose from the area being bombarded, and the shelling appeared to have set off at least two large secondary explosions.

Meanwhile, Sunni Muslim sheiks across Iraq planned to travel to Fallujah on Thursday for talks between the U.S.-led coalition, Iraqi authorities and local leaders to avoid what a key diplomat calls "a bloody confrontation" that could be "dramatic and long-lasting."

Fallujah is a Sunni stronghold that has been the scene of fierce anti-U.S. resistance in Iraq.

Marines launched an offensive against insurgents there this month after numerous attacks on American forces and others, including the March 31 killing and mutilation of four U.S. security contractors.

Clashes between Marines and insurgents have occurred daily despite a declared cease-fire and talks aimed at bringing stability and a return to local government control.

Marines said they've simply been responding to insurgent attacks and haven't shown a fraction of what they can do.

Additional violence was reported elsewhere in Iraq. A Ukrainian coalition soldier was killed and two others wounded in an ambush Wednesday in the area of As Suwaiyrah in Wasit province, the Polish-led command said.

Also Wednesday, a roadside explosion destroyed a U.S. shipment vehicle and wounded its driver in northern Baghdad, according to the U.S. military.

In remarks Tuesday to the U.N. Security Council on Iraq, U.N. special envoy Lakhdar Brahimi said a caretaker government could be selected by the end of May, a month before the June 30 handover of sovereignty by the coalition.

But Brahimi said the Fallujah stalemate, the U.S. standoff in Najaf with a Shiite Muslim cleric and other fighting bring an "atmosphere of great tension and anxiety."

Brahimi said the "hopes for a peaceful resolution" in Fallujah have not "yet been realized." A delegation from Fallujah met last week in Jordan with the staff of the U.N. Assistance Mission for Iraq, detailing the devastation the city has suffered, he said.

"This delegation claimed that several hundred of Fallujah's inhabitants had died and that well over a thousand had been wounded, many of them women, children and the elderly," Brahimi said.

"The U.N. is not in a position to verify these figures or the causes of death and injury. But there is little doubt that many lives have been lost and much suffering has been endured by civilians."

He said the United Nations has been pursuing restraint and working with humanitarian groups to provide relief.

The coalition, Brahimi said, "is well aware that, unless this standoff is brought to a resolution through peaceful means, there is great risk of a very bloody confrontation. They know as well as, indeed better than everyone else, that the consequences of such bloodshed could be dramatic and long-lasting."

The coalition is working on ways to re-establish local authority. Marines and members of the Iraqi Civil Defense Corps have begun rehearsal for joint patrols, which are soon set to begin in Fallujah.

While some families are trickling back into the city, many people have become displaced. The Iraqi Red Crescent is operating a camp in northern Baghdad, where at least 70 families have taken refuge.

In Fallujah, insurgents have distributed posters in Arabic and English offering a reward of $15 million for anyone who kills U.S. Defense Secretary Donald Rumsfeld, top commander Lt. Gen. Ricardo Sanchez and Army spokesman Brig. Gen. Mark Kimmitt.

Farther south, about 2,500 U.S. troops are poised outside Najaf, where an uprising led by radical Shiite Muslim cleric Muqtada al-Sadr began three weeks ago.

U.S. officials have said they want to capture or kill al-Sadr, who is wanted for questioning in the killing of a rival cleric last year. Talks aimed at defusing the possibility of fighting between U.S. troops and al-Sadr's militia, the Mehdi Army, are proceeding.

Troops from the U.S. Army's 1st Armored Division are picking up the slack left when most of the 1,430-strong Spanish contingent withdrew from the Kufa and Najaf area. Spanish Prime Minister Jose Luis Rodriguez Zapatero said Tuesday that all Spanish troops will be out of Iraq by May 27.

"Until the 27th of May the only Spanish military personnel remaining in zones of operation will be dedicated to security and to carrying out orders, support and logistics related to the withdrawal," Zapatero said.

American troops have moved into the Spanish base camp between Najaf and Kufa, a U.S. commander said.

Two sisters of a female soldier killed in Iraq have decided not to return to that country, a family spokeswoman said Tuesday.

Italian politicians condemned a threat Tuesday that Iraqi militants made to kill three hostages unless Italians protest over the presence of their country's troops in Iraq. Relatives of the hostages urged Italians to help set the men free and take part in rallies Wednesday and Thursday.

Halliburton Co. and its subsidiary Kellogg, Brown & Root confirmed Tuesday the death of an employee who has been missing since a convoy was ambushed April 9 outside Baghdad. The victim was identified as Tony Johnson, 47, of Riverside, California. Johnson was a volunteer worker, Halliburton spokeswoman Wendy Hall said. Thomas Hamill of Macon, Mississippi, and two other unidentified KBR employees remain missing since the attack.

Members of the International Committee of the Red Cross visited former Iraqi leader Saddam Hussein on Tuesday at an undisclosed location, according to a U.S. Army spokesman. Saddam has been in coalition custody since he was captured December 13. The last visit to Saddam from the Red Cross, which monitors conditions of prisoners of war, was in February.