One leaflet on the streets, purporting to be from the deposed Saddam Hussein's Baath Party, called for a general strike Saturday through Monday "to prove to our enemy that we are united people." The leaflet also said the day will mark the start of some kind of uprising.
In violence Thursday, Iraqi officers intercepted a motorist who tried to toss a hand grenade into a police station, an American solider was wounded when a bomb exploded near a U.S. Army convoy in the northern city of Mosul, and saboteurs bombed a train carrying Army supplies west of Baghdad.
An explosion shook Baghdad's old quarter, killing at least two people and triggering a large fire. It was unclear what caused the blast.
The U.S. command reported on Wednesday the number of attacks in the past week had jumped sharply to an average of 33 a day. That surge in violence led the United Nations to join the Red Cross and Doctors Without Borders in reducing Iraq staff.
Secretary-General Kofi Annan said the attacks in the last 72 hours appeared to signal "a new phase" in postwar violence.
In other developments:
"Obviously, a pullout from Iraq today would be catastrophic and would absolutely not correspond to the demands of the situation," he said. "We must…define an approach that will truly allow the Iraqis to take their destiny in hand."
The exodus of humanitarian workers came despite assurances by top U.S. administration officials — including Mr. Bush — that the security situation in Iraq was steadily improving.
It also followed a personal appeal by Secretary of State Colin Powell to the international Red Cross to remain in Baghdad because "if they are driven out, then the terrorists win."
The U.N. decision to pull its remaining international staff out of Baghdad was announced on Wednesday, two days after a deadly suicide car bombing at the Baghdad headquarters of the Red Cross.
"We have asked our staff in Baghdad to come out temporarily for consultations with a team from headquarters on the future of our operations, in particular security arrangements that we would need to take to operate in Iraq," U.N. spokeswoman Marie Okabe said.
She said it was not an "evacuation" and staff in the north would remain.
Okabe declined to give more details but about 60 U.N. staff members were believed to be in Iraq, including some 20 in Baghdad, after Secretary-General Kofi Annan ordered most others out in late September.
The United Nations scaled down its staff following the Aug. 19 truck bombing at its Baghdad headquarters that killed 23 people, including the top U.N. envoy to Iraq, Sergio Vieira de Mello, and a smaller blast near the U.N. offices last month.
The Red Cross said it would remain in Iraq but would scale back the number of international staff — now numbering about 30 — and increase security for those who stay. The agency has 600 Iraqi employees.
Asked on Thursday about U.S. pleas for the ICRC to stay put, the organization's Baghdad spokeswoman Nada Doumani said: "The ICRC will take its decision independently as it always had."
There was an apparent assassination attempt Wednesday night against an aide to Iraq's most influential Shiite Muslim cleric, Grand Ayatollah Ali Hussein al-Sistani.
The cleric, Abdel Mehdi al Karbali, suffered head wounds in the explosion of a hand grenade thrown at him and his bodyguards.