Loyalists of alleged al Qaeda chief in Iraq, Abu Mussab al-Zarqawi, claimed attacks on the heavily fortified central Baghdad compound housing the government and the US embassy and on the notorious Abu Ghraib prison.
Two drivers were shot dead trying to ram cars rigged with explosives into two high-profile targets. One was the high-security Green Zone, which holds the seat of the interim government and US embassy, and the other, to the west of the capital, the notorious Abu Ghraib prison, Iraqi and US sources said.
At least 13 people were killed, including two children, and 55 wounded during intense fighting around central Baghdad's Haifa Street, considered a bastion of Saddam loyalists, said the health ministry. The US military said six soldiers were also wounded.
Mazen al-Tomaisi, a Palestinian working for Saudi and Al-Arabiya television, died as he was reporting live from Baghdad during the clashes, a colleague said.
Heavy machine gun and assault rifle fire reverberated across Haifa Street for three hours and a tank was deployed to support US troops in an area that is perfect sniper territory with high-rise apartment blocks all around.
A car bomb exploded near the tank, setting it ablaze and witnesses said an angry mob pelted it with stones and danced around it. One man climbed on top, waving a black flag emblazoned with the name of Zarqawi's Tawhid-wal-Jihad group.
US helicopters then swooped down over the neighbourhood and fired missiles and heavy machine gun fire into the crowd, killing at least five people.
The US military said the tank was destroyed from the air "to prevent looting and harm to the Iraqi people".
Further north, three Polish soldiers were killed and three others wounded in an ambush near the city of Hilla, the Polish military said.
Also in the area, at least three national guardsmen were killed and three seriously wounded in a double car and roadside bomb attack, the Poles said.
In the West of Baghdad, 10 people were killed and 40 wounded as Sunni insurgents and US soldiers clashed in Ramadi, a medic said.
In a series of raids against Sunni insurgents in the capital, Interior Minister Falah al-Naqib said 16 out of 21 wanted suspects were arrested.
"They were all Iraqis, all of them. They are Sunnis. This is a war, so we have to get them," he said. During one of the raids to get them, a car bomb exploded killing an Iraqi police colonel, he said. A police lieutenant also died in the attack.
Another person was killed and 13 wounded, six of them national guardsmen, when a suicide bomber blew up his car near a mosque, said a doctor.
US Lieutenant Colonel Steve Boylan said that from late Saturday to early Sunday, more than dozen mortar rounds and rockets were fired into or around the Green Zone.
Police said that three Iraqis were killed when a roadside bomb intended for an American convoy blew up in the city of Samarra, where US troops recently returned for the first time since June.
Later, an apparent suicide car bombing also missed a US patrol and killed two civilians, police said.
In the northern city of Mosul, five policemen were killed and three wounded when gunmen attacked their patrol car, a medic said.
"Terrorist attacks in Iraq have killed more than 3,000 martyrs and wounded more than 12,000," Prime Minister Iyad Allawi told journalists in the main southern city of Basra, without specifying a timeframe.
Amid the violence, a persistent hostage crisis ground on with militants, according to a website statement, threatening to kill two Italian women if Rome did not recall its troops from Iraq within 24 hours.
"If we don't see the Italian troops withdraw from the land of Iraq, we will implement Allah's judgement on them, which will be slaughter," said the Islamic Jihad Organisation in Iraq.
In Italy, Foreign Minister Franco Frattini was poised for an 11th hour trip to the Middle East in a bid to help secure the hostages' release.