Photo show the "Green Zone" in Baghdad.

A suicide bomber Thursday managed to sneak in the heavily-fortified Green Zone in central Baghdad and blew himself up in Iraqi parliament complex, in defiance of new U.S. plan on curbing violence in the war-torn Iraq.

The suicide bomber wearing an explosive vest detonated in a restaurant inside Iraqi parliament complex while many members of parliament were having lunch after their ordinary session, killing eight people including three lawmakers, an Interior Ministry source told Xinhua.

Three legislators, four employees and the bomber himself were killed while 20 others including five lawmakers were injured, the source said.

The source only identified one of the dead legislator as Muhammed Hassan Awadh from the Sunni National Dialogue Front while keeping silent on the other two unfortunate lawmakers.

But according to local media, Taha al-Liheibi of the Sunni Accordance Front and Niamah al-Mayahi of the Shiite United Iraqi Alliance bloc were among the dead.

Mahmud al-Mashhadani, the speaker of the parliament, announced shortly after the bombing that the parliament will held an exceptional session Friday "as a challenge to terrorism."

U.S. ambassador to Iraq Ryan C. Crocker also issued a statement to condemn the attack "in the strongest possible terms." 

Photo shows the cafeteria in Iraq's parliament complex in Baghdad, Apr. 12, 207.

The parliament building is located in the heavily-fortified Green Zone. Thursday's blast is an extremely rare security breach in which a bomb was planted and detonated inside the exclusive area because anyone who wants to enter it must go through numerous security scrutiny, including dog sniffing and metal detectors.

The Green Zone has been in the past hit by indirect fires such as mortars, but they were all launched from places outside the enclave.

The deadly attack in Green Zone was not the only fatality in the capital as another suicide truck bombing happened hours before on a key bridge over Tigris River in northern part of the capital.

On Thursday morning, a suicide truck bombing hit the al-Sarafiya bridge, killing at least five people and wounding 18 others. The huge explosion totally damaged the steel structure of the bridge, sending at least five civilian cars tumbling into the Tigris River.

The al-Sarafiya bridge is a key artery in the northern part of the city. It is often used by minibuses and commercial vehicles travelling from central Baghdad to markets in the city's northern areas.

Thursday's suicide bombings came amid the two-month-old security crackdown in Baghdad, which is seen as the last chance to restore stability in the country.

So far, the crackdown has curbed some sectarian attacks and assassinations in the capital but failed to stamp out the violence in the areas outside Baghdad and on the rebound more attacks and violence occurred in those area.

The two suicide bombings, including one in the Green Zone, were undoubtedly a major setback for the U.S.-Iraqi forces crackdown even in the improving Baghdad.

Some analysts here said the insurgents wanted to send a clear message through the attack against the members of Iraqi parliament in the Green Zone that no one and no place in Iraq was safe and the ongoing crackdown was not working.

Editor: Yan