Two powerful car bombs have killed at least 21 people and injured dozens more in the Iraqi capital, Baghdad.
The second blast went off less than an hour after the first
The first bomb went off outside an army recruitment centre near an entrance to the high-security Green Zone in the centre of the city, witnesses said.
The second exploded as a US military convoy was passing along a main road on the east side of the river Tigris.
Bursts of gunfire were heard as a huge cloud of black smoke rose over the centre of the Iraqi capital.
In other developments on Monday:
- The Pentagon announced that 80 US soldiers were killed in Iraq in September, making it the second bloodiest month of the year after April, when 135 died
- US warplanes carried out pre-dawn raids on the rebel-held city of Falluja, killing at least nine people, hospital officials said
- A car bomb exploded near a primary school in the northern city of Mosul killing at least three people, Iraqi police said
- A director of Iraq's science ministry, Thamer Abdellatif, was shot dead on his way to work, along with a female colleague, the Iraqi interior ministry said
People who witnessed the first Baghdad bomb attack said the car raced towards the entrance of the Green Zone, which houses Iraqi government buildings and the US and British embassies.
It then detonated close to where recruits were lining up to join the Iraqi security forces.
Hospital and military officials said at least 15 people had been killed and more than 80 injured.
The BBC's Caroline Hawley in Baghdad says the injured were taken to hospital in cars and trucks, many of them with very serious wounds.
One doctor described conditions on the wards as "truly horrible", our correspondent says.
Less than an hour later, another explosion went off in the city's Saadoun Street, apparently targeting a US military convoy.
The Iraqi interior ministry said six people were killed and at least 12 injured in the second attack, most of them Iraqi bystanders.
Series of strikes
The US military says it has inflicted significant damage
on insurgent networks during weeks of "precision strikes" against targets in Falluja, which lies 65km (40 miles) west of Baghdad.
Casualties from Monday's raids included women and children, according to hospital sources.
The US military said it had hit a building where "anti-Iraqi forces" were moving weapons.
A second raid targeted followers of Jordanian militant Abu Musab al-Zarqawi, the military said.
Zarqawi's followers have claimed responsibility for a string of deadly bombings, kidnappings and other attacks in Iraq since the US-led occupation began.
A member of the Iraqi police force in Falluja told the BBC that the insurgents there included between 3,000 and 5,000 foreign fighters, from countries including Syria, Iran, Saudi Arabia and Afghanistan.
The Americans and Iraq's interim government say they are determined to retake rebel-held areas ahead of January's scheduled elections.
Meanwhile, US Defence Secretary Donald Rumsfeld said the coalition's assault on Samarra showed what had to be done to regain control of rebel-held parts of Iraq.
US and Iraqi government forces said on Sunday they had secured about 70% of the city of Samarra, after a two-day assault in which more than 125 insurgents had been killed and 88 detained.
Reports say residents of Samarra - which lies on the main highway from Baghdad to northern Iraq - are too afraid to venture out.
Witnesses in the centre of the city have spoken of American snipers shooting at anyone who appeared on the streets.
Some 5,000 troops poured into Samarra during Friday in one of the biggest operations since the invasion of Iraq.
"What has to be done in that country is what basically was done in Samarra over the last 48 hours," Mr Rumsfeld said.