Three US soldiers were among those killed in bold assaults on Iraqi security forces in Baghdad and the mainly Sunni cities of Baquba, Falluja and Ramadi.
Iraq's third-largest city Mosul was the worst hit, with suicide bombings killing 62 people and wounding 220, said a senior coalition military official.
He said the attacks showed signs of loose co-ordination between various groups intent on destabilising Iraq and warned of more bloodshed before and after the June 30 handover of power to Iraqis by the US-led administration.
"We would expect to see more activity like this as we get closer and closer to June 30, we don't think this was a one-off, we don't think this was an exception, we think we're going to see more of this," the official reporters.
"There's no reason to expect it will stop after June 30."
A group led by Jordanian militant Abu Musab Zarqawi, who Washington says has links to al Qaeda, claimed responsibility for the attacks in a statement on an Islamist Web site.
"Your brothers in Jama'at al-Tawhid and Jihad launched a wide assault in several governorates in the country which included strikes against the apostate police agents and spies, the Iraq army alongside their American brothers," it said.
"Your brothers in the martyrdom brigade also carried out several blessed operations including five in Mosul on Iraqi police centres, two in Baquba and another in Ramadi," said the statement, indicating that suicide bombers had carried out attacks in Mosul and elsewhere.
Iraq's Health Ministry had earlier put the death toll at 85 people and the number of wounded at 320.
Interim Prime Minister Iyad Allawi blamed a group linked to Zarqawi for multiple car bombings in the northern city of Mosul.
But he told a news conference that "remnants of the ex-regime", meaning Baathists loyal to ousted President Saddam Hussein, were behind attacks in Ramadi and Baquba.
But witnesses said some of the black-clad gunmen who attacked a police station and government buildings in Baquba, 60 km (40 miles) north-west of Baghdad, proclaimed loyalty to Zarqawi and wore yellow headbands linking them to his group.
It appeared to be the first time members of Zarqawi's underground network had surfaced in street combat.
"We think the Mosul incident was committed by Ansar al-Islam, which is a parallel organisation to the infidel Zarqawi," Allawi said of the bombings in the northern city.
STRICKEN CITY: At least seven large explosions shook Mosul, and local television stations ordered residents to stay at home. Police blocked all major roads and announced a dusk-to-dawn curfew.
The US military said an American soldier had been killed and three wounded in the blasts. It said a security guard was killed in a separate attack on a private security firm.
Gunfire rattled across Mosul as insurgents fought running battles with US troops and Iraqi police.
Fighting in Anbar province, which includes Falluja and Ramadi in the Sunni heartland's of central Iraq, killed at least nine people and wounded 27, the Health Ministry said.
Four Iraqi national guardsmen were killed and two civilians wounded by a car bomb blast in southern Baghdad, an officer in the force said. Hospital staff put the death toll at five.
The US Army said two soldiers had been killed and seven wounded in an ambush in Baquba. The Health Ministry said 13 people had been killed and 15 wounded in the town.
US air strikes destroyed three buildings that guerrillas were using to fire on 1st Infantry Division soldiers and Iraqi security forces near Baquba's sports stadium.
Many fighters wore headbands marked "Saraya al-Tawhid wal-Jihad" (Battalions of Unification and Holy War), a name that closely resembles Zarqawi's Jama'at al-Tawhid and Jihad group.
They handed out leaflets warning Iraqis not to work with US-led occupation authorities. "The flesh of collaborators is tastier than that of Americans," the leaflets said.
Zarqawi's group has claimed many attacks in Iraq, including this week's beheading of a South Korean hostage. The United States has offered a $10 million reward for Zarqawi's capture.
In Ramadi, insurgents fired mortars at two police stations and the governor's house in Ramadi, 110 km (68 miles) west of Baghdad. Allawi said the governor was not there at the time.
The US military said seven Iraqi police and 12 insurgents had been killed in the fighting.
Fierce clashes raged for two hours in Falluja where US Marines called in air strikes by planes and helicopters on guerrilla targets in the rebellious town west of Baghdad.
A US Cobra helicopter was shot down during the fighting but the crew walked away unhurt, Marines said. Allawi's government takes over when the US-led occupation formally ends on June 30, but a multinational force of more than 160,000 mostly US troops will stay on to support it.
Iraq's fledgling security forces, the main target of the violence, are crucial to the new government's prospects for imposing order after the handover.