At least 26 people have been killed in a suicide bomb attack on an Italian police base in the southern Iraqi city of Nasiriya.
The entire front of the three-storey building was blown off
Sixteen of the dead were Italian military personnel, while two Italian civilians and eight Iraqis also died.
The attack - among the worst on foreign bases in Iraq - marked Italy's first deaths in hostile action there.
A series of blasts were heard after nightfall in Baghdad but may have been connected to a US military operation.
The Pentagon said forces of the First Armored Division had been deployed to destroy a facility used by anti-coalition rebels. It gave no further details.
Responding to the Nasiriya attack, Italian Prime Minister Silvio Berlusconi said it would not affect Italy's commitment to the US-led coalition.
And Paul Bremer, the head of the US administration in Iraq, said "terrorists" would not drive US forces out of the country.
He said the bombings hurt Iraqis most of all.
"Obviously the terrorists are trying to encourage the Iraqi people to believe that the United States is not
going to stay the course. They've killed mostly Iraqis," he said in Washington.
MAJOR POST-WAR ATTACKS
2 November: 16 US soldiers die as Chinook helicopter downed
27 Oct: Red Cross and other buildings in Baghdad bombed, more than 30 killed
12 Oct: Baghdad Hotel bombed, six dead
9 Oct: Police station in Baghdad bombed, 10 killed
29 Aug: Mosque near Najaf bombed, dozens dead including Shia Islam's top cleric in Iraq
19 Aug: UN headquarters in Baghdad bombed, 23 killed including head of mission
7 Aug: Jordanian Embassy bombed, 14 killed
At least 180 Iraqis have died in attacks on such targets as the United Nations and Red Cross.
The BBC's Paul Adams at the scene says the attack was quite sophisticated.
He says witnesses reported that gunmen opened fire on the entrance to the compound, allowing a petrol tanker to ram the gates before exploding in a ball of fire.
The entire front of the three-storey building was ripped off, and there are fears that some of the victims might still be buried in the rubble.
Arc lights have been set up to help rescuers, who are still digging through the rubble, our correspondent says.
The force of the blast - which occurred at about 1030 local time (0730GMT) - blew out windows in another building across the Euphrates river.
About 80 Iraqis and 20 Italians were injured in the explosion.
A post-war deployment of about 2,400 Italian military personnel serves under British command in southern Iraq as part of the US-led coalition.
In Italy, President Carlo Azeglio Ciampi called the bombing a "terrorist act" and said the officers were killed "in carrying out their duty to
help the people of Iraq recover peace, order and security".
"Our carabinieri, our armed forces are in Iraq by a mandate and
the will of parliament," he said. "All of Italy is behind them
and supports them in this bitter trial."
The Pope condemned the bombing, describing it as a "vile attack" against a mission
Mr Berlusconi said the attack would not derail Italy's
commitment to helping Iraq, but the Italian opposition has demanded the withdrawal of the country's troops from Iraq.
"They were sent to an Iraq in flames because the government
wanted to do a favour for the Bush administration without taking
risks into consideration," said Pietro Folena of the main
opposition party, the Democrats of the Left.
"Now the Italian
soldiers must come home. It is the only right thing to do at
Defence Minister Antonio Martino said fighters loyal to deposed Iraqi leader Saddam Hussein were behind the attack.
"Evidence on the ground and intelligence reports lead us to
believe that today's attack was planned and carried out by
remnants loyal to Saddam... united with Arab extremists,"
he said in an address to the Italian Senate.
US soldiers killed
Vehicle bombs have been used in attacks on numerous organisations in Iraq since the war ended, including the United Nations and the International Red Cross.
Nasiriya, a Shia Muslim city which saw heavy fighting during the war, had been relatively quiet in
However, the BBC's Peter Biles says the bombing of a minibus in Basra on Tuesday and the killing of a Polish soldier near Karbala last week point to a possible upsurge of attacks in southern Iraq.
Elsewhere in Iraq, the US military says two of its soldiers have been killed in separate bomb attacks in and around Baghdad.
More than 150 US troops have been killed in attacks since major combat operations in Iraq ended.