A suicide bomber killed eight people in the Iraqi parliament Thursday, 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 had been killed and 20 wounded in the blast which tore through a cafeteria where many lawmakers were having lunch. State television said at least three of the dead were lawmakers.

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-Qaida.

"My message to the Iraqi government is 'We stand with you,'" the US president said.

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.

A truck bomb also killed at least seven people on Sarafiya bridge in northern Baghdad, a main artery linking east and west Baghdad, destroying most of the steel structure and sending several cars plunging into the River Tigris below.

One army officer on the scene said explosive charges might have also been used to bring down the bridge that local residents said was built by the British in the early 1900s.

Among the dead were four policemen who drowned after their car toppled into the river's muddy waters, police said.

How explosives were smuggled into the Green Zone is likely to be the focus of an investigation. The explosives 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.

The US military said earlier this month that two explosives vests were found in the zone. A third suspected vest was known to been missing and a hunt was launched to find it.

A witness said the explosion took place at the cashier's register in the cafe, which is near parliament's main assembly hall. Parliament was in session Thursday.

"I saw a ball of fire and heard a huge, loud explosion. There were pieces of flesh floating in the air," said a witness who was lightly wounded in the arm.

Officials named Mohammed Awadh, a member of the Accordance Front, the biggest Sunni bloc in parliament as one of the dead lawmakers. Another parliamentarian was missing and presumed dead. Two other lawmakers were critically wounded.

Militants have rarely managed to penetrate the various checkpoints and carry out attacks inside the zone, although the area has come under increasing rocket and mortar attack in recent weeks.

In the deadliest bomb attack in the Green Zone, two Al-Qaida bombers blew themselves up at a restaurant and a nearby street in October 2004, killing five people, including three Americans.

One of Iraq's vice-presidents survived a bomb attack at a government ministry outside the Green Zone in February. A deputy prime minister was wounded last month in a suicide bomb attack at a prayer hall in his compound in the capital.

US Secretary of State Condoleezza Rice said Thursday's attack was carried out by those "who wish to stop the Iraqi people having a future that would be based on democracy and stability".

She said the Baghdad security plan was in its early stages and "we have said there will be good days and bad days".

(China Daily via agencies April 13, 2007)