The Iraqi parliament convened a special session today to condemn yesterday's lunchtime suicide attack which killed an MP and left 23 people injured.

The assembly’s speaker, Mahmud Mashhandani urged members to stand strong in the face of the violence, for which an al-Qaeda backed group has claimed responsibility, but there were a number of empty seats in the chamber as he called for unity.

“This meeting is a clear message to all terrorists and to everyone who tries to halt this blessed process, which we should sacrifice ourselves for,” he said. “You are capable of shouldering every difficulty.”

The attack, which took place in the parliamentary cafeteria, killed Mohammed Awad, a member of the National Dialogue Front, a Sunni party. It has raised alarm bells about how effective security is within the heavily protected Green Zone.

Tighter restrictions were in place today, as only members of parliament and the state media were allowed to attend the session. While it was initially suggested that the bodyguard of an MP was responsible for the blast, three cafeteria workers have been arrested in the continuing investigation and a group that calls itself the Islamic State in Iraq has claimed responsibility using a statement online.

“Whether we are in or out of the government and the political process, we have to find a solution to national reconciliation,” Shia Vice President Adel Abdul-Mahdi, who survived an assassination attempt in February, told parliament.”

Previous calls for unity by Iraq’s leaders have mostly fallen on deaf ears as sectarian violence has spiralled. “This is undeniably a difficult blow, but it should unify us to confront the evil of terrorism and it proves that terrorism is indiscriminate - Sunnis, Shias, Kurds and Arabs were maimed in this attack,” Deputy Prime Minister Barham Saleh, a Kurd, added.

James Hider, The Times’ correspondent in Baghdad, has observed significant flaws in the security that surrounds the parliamentary buildings: “There is a tradition among the police of taking a softer view of security surrounding those with status,” he said. “Politicians complain about getting frisked, so security can be pretty slack around those who are higher up in particular.”

He points to a lack of communication between security forces and MPs individual security arrangements as other possible avenues of investigation. “The Shias are very suspicious of the Sunnis who have come in from insurgency linked groups. They don’t trust the police, so they come in with their own security people. It creates a fairly poisonous atmosphere."

The bombing has defied a new security crackdown and left American forces concerned as to how it can have occurred: “It’s very troubling that this happened inside the Green Zone. And we’re going to work to make sure that, one, we find out how it happened and that it doesn’t happen again,” said Dana Perino, spokeswoman for President Bush.

Nuri al-Maliki, the Iraqi Prime Minister, who is in South Korea, condemned the attack and called for a criminal investigation into those responsible.

The bombing was the most spectacular breach yet of the multiple layers of security in the Green Zone, but elsewhere in Iraq, members of the public were more concerned about the explosion that destroyed the Sarafiyah bridge yesterday, killing at least seven people.

The bridge, over the River Tigris, was a major link between the Shia east and the Sunni west, and its destruction effectively cuts the areas off from each other, leaving many travelers without a safe an alternative way to get to work or study.

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