Saboteurs brought a trainload of U.S. Army supplies to a fiery halt west of Baghdad on Thursday, as a Ramadan (search) campaign of terror bombs and escalating attacks spurred a new Iraq pullout by international aid groups.

An explosion rocked a row of shops in Baghdad's Old City (search) late Thursday, killing two people, according to police, and deepening the unease in the Iraqi capital.

Many Baghdad parents apparently were keeping their children home from school out of fear of further bombings like the four that killed three dozen people and wounded more than 200 across the capital on Monday, start of the Muslim holy month of Ramadan.

"We heard rumors about big bombs that will go off," said Duha Khalid, 18, most of whose friends stayed home Thursday from her girls' high school, situated near a police station.

The police, prime targets in the bombings Monday, were targeted again Thursday, when officers intercepted a motorist who tried to toss a hand grenade into a police station on the edge of Baghdad's heavily guarded "green zone," the headquarters enclave for the U.S. occupation.

As October's heat finally gave way to cooling winds off the desert, rumors of looming trouble spread through this city of 5 million, focusing on the start of the week -- Saturday in Muslim Iraq.

One leaflet on the streets, purporting to be from Saddam Hussein's Baath Party (search), called for a general strike Saturday through Monday "to prove to our enemy that we are united people."

The plainly typed flyer will further feed the debate over the identity of the shadowy underground of bombers striking Iraqi cities and ambush teams harassing U.S. forces: Are they die-hard Baathists, other anti-U.S. nationalists, foreign Islamic fighters, or some combination?

The identity of those swarming over the sabotaged train Thursday was clear: they were Iraqis from the Fallujah area, 35 miles west of Baghdad, who fell upon the crippled train to loot it of computers, tents, bottled water and other Army supplies.

The goods had been bound for the town of Haditha, 100 miles up the Euphrates River from Fallujah, when a makeshift bomb exploded along the tracks four miles west of Fallujah. As the uninjured engineer fled, four shipping containers on flatcars went up in flames, and more than 200 area residents descended on the other cars to make off with whatever they could carry.

No U.S. forces came to the scene, but at one point the looters scattered when two American helicopters whirred in for a look. At another point, Iraqis backed trucks up to the bombed train to offload goods.

The 6-month-old U.S. occupation is highly unpopular in Fallujah and in much of the rest of Iraq's Sunni Muslim heartland, a favored region under the Baathist regime toppled by the U.S.-British invasion force last April.

Monday's bombings, one of which devastated the Baghdad headquarters of the International Committee of the Red Cross, prompted international aid organizations to quickly review their presence in Iraq.

On Wednesday, the ICRC announced it would reduce its 30-member international staff in Iraq but would continue operations. Among other things, the Red Cross, which has 600 Iraqi employees, tries to ensure the rights of prisoners of war and other postwar detainees, has worked to improve water quality, particularly for hospitals, and delivered medical supplies to Iraqi hospitals.

A smaller medical aid group, Medecins Sans Frontieres -- Doctors Without Borders -- also said it was pulling its international staff out.

But the Italian Red Cross said Thursday its workers will remain in Iraq.

"We continue our activity," said Marino Capece Minutolo, director of the Italian mission. "We don't care about bombs and terrorists because we have a job here, a very important job."

Also Wednesday, the United Nations, whose Baghdad headquarters was devastated by a bombing in August, said it will temporarily withdraw its remaining international staff from Iraq -- approximately 60 people, including 20 in Baghdad. The U.N. staff in relatively peaceful northern Iraq will remain.

"It's not our intention now to pull out totally," U.N. Secretary-General Kofi Annan told The Associated Press in New York on Thursday. "Of course, it depends on what further developments are coming." "We want to reassess our position and our posture and also try and assess the new developments on the ground," Annan said, "because we seem to be entering a new phase with the attacks of the last 72 hours, and we need to analyze for ourselves what the future holds and how we should conduct our own operations."

"I think this sort of reflection is better done in a calmer place and then we determine what our next moves should be," he said.

The U.S. command reported Wednesday that the number of attacks in the past week had jumped sharply to an average of 33 a day. In one incident early Thursday, a bomb exploded near a U.S. Army convoy in the northern city of Mosul, slightly wounding a 101st Airborne Division soldier.

In other developments:

-- A hand grenade blast in the southern city of Karbala late Wednesday wounded Sheik Abdul-Mahdi al-Karbalai, a representative of Shiite Muslim leader Ayatollah Ali al-Sistani. Rivalries among Shiite factions have led to occasional bloodshed since the war's end.

-- Early Thursday, U.S. 4th Infantry Division soldiers raided a half-dozen houses in Tikrit, Saddam's hometown, and detained four people suspected of planning attacks on U.S. forces.

-- Iraqi oil officials said bad weather halted exports of crude oil from its southern Basra terminal for three days. Iraqi and U.S. officials are counting on oil revenues to help boost Iraqi reconstruction.