Most of the deaths were in the northern city of Mosul, where 62 people were killed and 216 injured in a string of car bombings of police buildings.
Apart from the Iraqi casualties, the US military said an American soldier was killed and three wounded in the blasts. It said a security guard was also killed.
Clashes also occurred in Baquba, Ramadi, Baghdad and other areas.
The extent of the attacks is a clear sign of just how powerful the resistance to US-led occupation in Iraq remains - and could be the start of a new push to torpedo the 30 June transfer of authority to an interim transitional government.
Iraqi prime minister Iyad Allawi said he did not believe the attacks were coordinated. Although acknowledging the attacks had the fingerprint of foreign resistance fighters, he added that former Baathists loyal to Saddam Hussein were probably behind the violence in Ramadi and Baquba.
Iraqi police - entrusted to take a larger role in security after the handover of power - appeared outgunned and unable to hold positions in most of the cities under fire.
American troops raced to offer support, using aircraft, tanks and helicopters to repel the attacks.
The heaviest fighting raged in Baquba, 60km northeast of Baghdad, where two American soldiers were killed and seven were wounded, the US 1st Infantry Division said.
Scores of black-clad men swarmed on to targets in the city, which included a police station and government buildings.
US aircraft dropped three bombs
near the Baquba soccer stadium
Resistance fighters roamed the city with rocket launchers and automatic weapons, seized two police stations and destroyed the home of the police chief of surrounding Diyala province.
US aircraft dropped three 500-pound bombs near the Baquba soccer stadium, said Major Neal E O'Brien, a US 1st Infantry Division spokesman.
At the main hospital in Baquba, doctors struggled to deal with a steady stream of wounded. Doctors stood in pools of blood. Civilian cars, including pickup trucks, raced to the door of the emergency ward bringing people with gunshot and shrapnel wounds.
By evening calm had returned to the town, according to Aljazeera correspondent Imad al-Atrash.
"The town is completely deserted. US forces have closed the most entrances. There is no shooting".
Al-Atrash said 66 wounded had arrived at the hospital while the number of dead remains unknown.
US gunships flew low over Baquba, some swooping down on suspected hideouts of resistance fighters in palm groves. US forces claimed to have killed 20-30 insurgents.
Some motorists flew white flags from atop their cars to ensure their safety. US tanks, some firing their machine-guns, moved into the city centre by the afternoon.
In Baghdad, four police stations
and a military convoy were hit
In Baghdad attackers set off an explosion as a military convoy passed, injuring one soldier.
Also in Baghdad, resistance fighters attacked four Iraqi police stations using mortars, hand grenades and AK-47s on Wednesday and Thursday. Police fought back, and defended the stations with minimal assistance from occupation forces, a US statement said.
And in Ramadi, 110km west of Baghdad, US sources said eight people were killed when armed fighters attacked two police stations and the residence of a security official
A group headed by al Qaida-linked operative Abu Musab al-Zarqawi claimed responsibility for Thursday's attacks.
"Your brothers in Jamaat al-Tauhid 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," said the statement reportedly posted on an internet website.
"Your brothers in the martyrdom brigade also carried out several blessed operations including five in Mosul on five Iraqi police centres, two operations in Baquba and another in Ramadi," said the statement, whose authenticity could not be immediately verified.
PM Iyad Allawi said Thursday's
attacks were not coordinated
To the west of the capital, explosions and shelling shook Falluja. By late afternoon, calm had returned to the town after an unconditional ceasefire was agreed upon.
Mahmud Ibrahim al-Jiraisi, governoer of Falluja, told Aljazeera that he headed a delegation which included the head of the local council, military, police civil defence officers and tribesmen, which negotiated with the US army.
"The talks were successful," al-Jiraisi said. "We agreed on an unconditional ceasefire. We called on them to open the roads leading to Falluja, particularly the highway, the old road leading into the city and the checkpoint at the eastern entrance to the town."
"Life has returned to normal," he added.
US forces have launched two airstrikes on Falluja since Saturday against what they said were safehouses for al-Zarqawi.
Local residents have said mostly civilians died in the attacks.