At least 26 people have been killed in a series of car bombings in Baghdad, US military officials in Iraq say.
US soldiers sealed off the area near the Australian embassy
Four of the blasts happened within 90 minutes of each other, targeting local and foreign security forces. Iraqi officials say only 13 people died.
A group linked to suspected al-Qaeda leader Abu Musab al-Zarqawi said it carried out several of the attacks.
The blasts came a day after Iraq announced new measures to boost security for elections on 30 January.
The BBC's David Willis in Baghdad says it seems to be one of the most violent days in the capital for several weeks.
Grim predictions of an escalation in violence in the run-up to the elections appear to be coming true, our correspondent adds.
In other developments:
- Two Iraqis said to be working for a US firm involved in preparations for the Iraqi elections are shown being killed by militants in a video on the internet
- Two employees of a British security company killed in attack near Beiji, US military says
- A roadside bomb hits a military convoy south of Baghdad, injuring one soldier
- An influential group of Muslim scholars calls for the release of all hostages on the eve of the Muslim festival of Eid.
The spate of attacks began when an explosion rocked the Australian embassy at about 0700 local time (0400 GMT).
BAGHDAD CAR BOMBS
1. Two killed near Australian embassy, Babil district
2. Eighteen killed near police post and hospital, Karrada/Alwiya
3. Two killed south of Baghdad International Airport
4. Four killed at disused Muthanna airfield, Salam
5. One killed at bank and mosque, Utafiya
Source: US military
Policeman Hussein Ali said a suicide bomber rammed his vehicle against sand barriers and blast walls in front of the building, AFP news agency reported.
Two Iraqis were killed and two Australian soldiers were slightly injured, the Australian military said.
Australia, a staunch US ally, was one of the first countries to join the US-led invasion of Iraq, but has since scaled back its forces there.
The heaviest casualties on Wednesday appear to have occurred when a car blew up not long afterwards near a police station in the eastern Karrada district of Baghdad.
The US military said 18 people, including five Iraqi police officers, were killed.
A statement from a group linked to Zarqawi said "martyrdom squadrons" had struck the Australian embassy and two police stations.
BLOODY DAYS IN BAGHDAD
3 Dec 2004 : 26 die in attacks on a mosque and a police station
11 Nov : A car bomb in a commercial area kills 17 people
30 Sept : Bomb blasts kill at least 41 people, including 34 children
14 Sept : A car bomb explodes near an police station, killing 47 people
17 June : Car bombs kill 41 people, including 35 at an army recruiting centre
Zarqawi has been blamed for numerous deadly attacks in Iraq since the US-led war was declared effectively over in May 2003.
Car bombs driven by suicide attackers have become a feature of the insurgency against US-backed authorities.
Iraqi officials said on Tuesday they would close all the country's land borders for three days around the 30 January elections.