U.S. military forces and Iraqi police pushed back Friday against an insurgency that a day earlier orchestrated attacks across central and northern Iraq, striking a suspected safe house in Fallujah and reoccupying two police stations in Baqubah that had been in the hands of armed guerrillas.

In Baghdad, meanwhile, officials of the interim government set to assume political power from the U.S.-led occupation next week said they may impose emergency rule in parts of the country if the violence continues. Warning of the influence foreigners are exerting on the insurgency, the officials called on all Iraqis to join the fight against an anti-occupation campaign whose effectiveness has surprised U.S. military commanders.

"Today is a day for the Iraqi people to say to these traitors: The time has come for a duel, and with God's help it will be a great duel, a great contest in which the Iraqi people will ultimately be victorious," said Hazem Shalan, the country's defense minister.

The surprise attacks across six cities and towns on Thursday appeared to have exposed for many Iraqis the vulnerability of the incoming government, which is scheduled to assume political authority on Wednesday after a 15-month occupation. But Iraqi officials sought to turn the uprising to their political advantage Friday by accusing foreign Arab fighters of carrying out the attacks that killed more than 100 Iraqis and three U.S. soldiers, while offering little evidence to support the claim.

U.S. warplanes dropped precision-guided bombs for the third time this week in a neighborhood of Fallujah, the city 35 miles west of Baghdad that has long been hostile to the U.S.-led occupation. Twenty people were reportedly killed. Marine tanks took up positions on the outskirts of the city, witnesses said, and traded sporadic gunfire with men inside.

U.S. military officials said the target was a safe house used by militants associated with Abu Musab Zarqawi, a Jordanian whose group asserted responsibility for the previous day's attacks. U.S. and Iraqi officials say Zarqawi is affiliated with Osama bin Laden's al Qaeda network, and they have blamed him for a string of car bombings targeting supporters of the occupation and for the beheading of an American businessman, Nicholas Berg.

In Baghdad, where a roadside bomb killed an Iraqi policeman and wounded another on Friday, the country's new defense and interior ministers assured Iraqis that the interim government would take firm action against all members of the insurgency. U.S. and Iraqi officials have said the resistance consists of sympathizers of ousted president Saddam Hussein's Sunni Muslim-led government, disaffected Shiite Muslims and foreign Arabs who have come to fight the American project.

The interior minister, Falah Naqib, warned that he may impose emergency laws in some or all of the country. He called on the Iraqi people to help security forces "remove this cancer from their midst" by informing authorities of insurgents' whereabouts.

Shalan said Iraqi authorities would decide whether to impose an emergency decree "based on the degree of danger" and acknowledged that they had drawn up "an urgent plan for Baghdad and other provinces."

Among the plan's provisions, officials said, is the deployment of a 1,000-member counterinsurgency task force in the capital to work alongside U.S. forces. The unit, part of an Iraqi army that has fewer than 5,000 soldiers, is completing training at a base north of Baghdad.

Shalan said the emergency declaration was being contemplated in part because of public pressure for strong action by the government to restore order. But with U.S.-led military forces effectively in charge of Iraq's security, it was not immediately clear what impact -- other than a symbolic one -- such a declaration would have.

Some Iraqi officials suggested it would allow authorities to impose curfews and detain suspected insurgents without bringing them before an Iraqi judge, effectively extending certain provisions of martial law put in place during the U.S. occupation.

Although declaring an emergency could prove popular with Iraqis who support aggressive measures to combat violence, it would reprise a tactic used by Hussein as a cover for rampant human rights abuses.

In an interview published Friday in the German newspaper Die Welt, Secretary of State Colin L. Powell said such a declaration "would make our task in Iraq more complex, because applying martial law is more a police problem than a military one -- at least one would hope so."

Shalan said the decision would be made by Prime Minister Ayad Allawi and President Ghazi Yawar, in conjunction with other top security officials.

Here in the city hit hardest by Thursday's violence, streets that had been the scene of battle returned to an uneasy quiet. But just before 8 a.m. on Saturday, explosions and small-arms fire erupted downtown in an apparent attack on an Iraqi police station.

Col. Dana J.H. Pittard, commander of the 1st Infantry Division's 3rd Brigade Combat Team, said the skill that insurgents displayed Thursday was likely intended only as a test for U.S. forces. The day-long fight downtown killed two U.S. soldiers, 17 Iraqi police officers and more than 30 insurgents -- none of whom turned out to be foreign, he said.

Pittard said intelligence reports suggested that the insurgents were planning a fresh offensive to occupy government buildings, which he described as the "symbols of authority and authority in the city," before the official end of the U.S. occupation.

"If that was their attempt at a Tet Offensive, it was a yawner," Pittard told reporters here. "But it may have been a tactic to see how we would react. We have to give our enemy more credit."

Pittard said Iraqi police had reoccupied two police stations overrun the previous day. U.S. commanders said the police did so without fighting and that the insurgents may simply have abandoned the stations after stealing the assault rifles inside.

Chandrasekaran reported from Baghdad.

Sunni Muslim Iraqis pray at Baghdad's Abu Hanifa mosque, where the imam denounced the continued killing of Iraqi security forces by insurgents. Iraqi officials have sought to blame foreign Arab fighters for many of the attacks.A policeman inspects damage a day after a car bomb demolished the police station in the northern city of Mosul.