A suicide bomber killed eight people in the Iraqi parliament, slipping through multiple checkpoints in a brazen strike that challenged a major security crackdown in Baghdad.
US military spokesman Major-General William Caldwell said eight people had been killed and 20 wounded in the blast, which tore through a cafeteria where many MPs were having lunch.
Iraqi security officials believe the suicide bomber was a Sunni MP's bodyguard. State television said at least three of the dead were MPs.
It was the most serious breach of security in the Green Zone, the sprawling, heavily protected area in central Baghdad that houses parliament, government offices and the US embassy.
US President George W Bush and Iraqi Prime Minister Nuri al-Maliki, who is on a trip to the Far East, condemned the attack, which Caldwell blamed on Sunni Islamist al-Qaeda.
The bold attack by a suicide bomber wearing an explosives vest came despite a two-month-old operation by thousands of US and Iraqi troops in the capital regarded as a last chance to stop a slide to full-scale sectarian civil war.
How explosives were smuggled into the Green Zone is likely to be the focus of an investigation.
They would have had to pass through an outer checkpoint manned by US and Iraqi troops and multiple inner checkpoints guarded by security contractors and foreign troops that are part of the US-led coalition.
US Secretary of State Condoleezza Rice condemned the attack saying: 'It is obviously again the terrorists and those who wish to stop the Iraqi people from having a future that would be based on democracy and stability.
A suicide bomber earlier blew up a truck on a bridge over the Tigris river in northern Baghdad.
The explosion partially destroyed the bridge, killing at least eight people. Another 26 people were injured and 20 cars fell into the river below.
The morning rush hour attack came a day after US military for the first time charged that Iran was supporting Sunni extremist groups.
The bombing ripped through the metal Al-Sarafiyah Bridge, which connects the Shia Al-Atafiyah neighbourhood on the western bank of the Tigris to the Sunni area of Waziriyah on the east.
US troops face longer duty
The US Defence Secretary, Robert Gates, announced last night that US troops in Iraq and Afghanistan will have their tour of duty extended from 12 to 15 months.
Mr Gates said it would allow the Pentagon to keep troop levels stable in both countries for another year.
However, commentators said the decision may intensify demands from Congress for a timetable under which US troops would start leaving Iraq next year.
Mr Gates told reporters that the measure was a response to the pressure the US military was working under.
