With potential food shortages just weeks away, the U.S. military opened a warehouse to U.N. aid shipments Sunday, stockpiling flour for Baghdad's people as workers pressed to restore battered basic services like power and water.

An opposition figure who has proclaimed himself mayor said he had formed a municipal government. He promised to put on trial anyone whose "hands are stained with the blood of the Iraqi people" under a new constitution based on Islamic law.

Recently returned exile Mohammed Mohsen al-Zubaidi said he had held meetings to draft new statutes in a country that has spent decades answering to only one authority -- Saddam Hussein.

"We have met with lawmen to create laws, and to open the courts so that life can begin to take on legitimacy," al-Zubaidi said at a news conference.

Without elaborating, he said Iraq's new constitution would be based on Islamic law, as many Arab nations' constitutions are to varying degrees. The comment drew applause from Arab journalists gathered in a sweltering coffee shop.

"Every person whose hands are stained with the blood of the Iraqi people will be put on trial," al-Zubaidi proclaimed.

Islam is the official religion under Iraq's current constitution, but followers of other faiths have freedom to practice.

But as Baghdad's Christians celebrated Easter, they voiced fears that a government run by the Shiite Muslim majority could limit those freedoms.

"If they come to power, we'll leave the country," electrician Jacob Koda, 51, said in the courtyard of Baghdad's Sacred Heart Church.

Al-Zubaidi and the leader of his U.S.-backed Iraqi National Congress, Ahmad Chalabi, are both Shiite Muslims. But Chalabi told ABC-TV's "This Week" on Sunday that he does not envision an Islamic theocracy, although religious groups would likely play a role in governing Iraq.

"There is a role for Islamic religious parties," he said from Baghdad. "But they are not going to be forcing any agenda or forcing a theocracy on the Iraqi people."

Fifty trucks loaded with 1,400 tons of wheat flour -- the first substantial convoy of World Food Program aid -- arrived from Jordan at a Trade Ministry warehouse on Sunday.

U.N. officials have said most Iraqis had enough food stores to last them until late April.

Electrical engineers again held out hope for an end to Baghdad's paralyzing two-week power outage, saying a bombed pipeline had been fixed and the lead power plant could be back on line by the end of the day.

Oil Ministry officials told engineers at the southern al-Doura power plant that they had replaced a bombed five-foot stretch of pipeline supplying fuel to the plant, said Janan Behnam, chief engineer and manager of the plant. But some engineers said they were skeptical.

Stores were open and the streets of Baghdad crowded as residents began sweeping up debris and cleaning their homes. The coalition-run Information Radio announced an 11 p.m.-6 a.m. curfew for the capital.

"Anyone who violates this curfew will put himself in danger," the announcer said. Another announcer told people not to carry weapons "because you might be considered a threat to coalition forces."

As U.S. Marines left their area of control in eastern Baghdad, departing toward southern Iraq, a smaller number of Army soldiers moved in from across the river to keep the peace. They are being aided by hundreds of Baghdad police officers slowly returning to their jobs.

Dozens of jobseekers milled outside Baghdad's Alwiyah Country Club hoping for work, though it was unclear who was taking down their names. "We just want to work. ... anything you want," said Ali Kalaf, a 22-year-old student.

Days after al-Zubaidi essentially proclaimed himself mayor of Baghdad, it remained unclear where his authority comes from -- or if it actually exists. No U.S. officials were present at his news conference in the Palestine Hotel.

"I was chosen by tribal leaders and educated people, the doctors of the city and other prominent figures," al-Zubaidi said. "We are not a transitional government. We are an executive committee to run Baghdad."

Baghdad currently has no government. U.S. forces, together with returning Iraqi police, are keeping the peace until they can arrange for an interim civil authority, expected to be led by retired U.S. Lt. Gen. Jay Garner. He was scheduled to pay his first postwar visit to Baghdad on Monday.

But al-Zubaidi said Sunday that 22 committees had been formed to administer Baghdad, and people had been appointed to lead them.

He urged people working in Iraq's ministries to return to their jobs and predicted radio, television and the Iraqi News Agency would all be running on Monday. He said enough funds remain in government coffers to pay civil servants' salaries, though he didn't say for how long.

Gen. Jawdat al-Obeidi, an aide to al-Zubaidi, said police acting on a tip from a "good citizen" had discovered a house used by Saddam's intelligence services suggesting government sponsorship of terrorists around the world. He gave few details.

He said police opened safes there and they found "many documents, lists of terrorist networks, intelligence elements, officers responsible for killing innocent people all over the world, assassination attempts, lists of their payments and bank accounts to finance those terrorist networks."

Time magazine, meanwhile, reported that an iron maiden -- a sarcophagus-like chamber with spikes inside -- was found in the office of the Iraqi Olympic Committee, which was headed by Saddam's son, Odai. Reports have circulated that Odai tortured athletes who displeased him.