Iraq's parliament has held a special session in a defiant response to a suicide bombing inside its building.
Turnout was low because of a travel curfew, but those present said it was a message to all "terrorists".
One MP has been confirmed dead. Initial reports by the US military said eight people had died - three of them MPs.
An Iraqi umbrella group of insurgent movements believed to be linked to al-Qaeda said it was behind the attack in the heavily-fortified area.
"A knight from the state of Islam... reached the heart of the Green Zone" and exposed the truth about the US-led security surge in Baghdad, said the Islamic State in Iraq in its claim posted on an Islamist website.
It is impossible to say whether the claim is genuine but one institute which monitors militant websites believes that it is, says the BBC's Jonathan Charles in Baghdad.
It is also the sort of headline-grabbing attack carried out by the organisation in the past, our correspondent adds.
The rare emergency session - on what is normally a rest day - was called by parliament's speaker to "defy terrorism".
Opening the meeting, speaker Mahmoud Mashhadani said it was "a clear message to all the terrorists and all those who dare try to stop this (political) process".
"We ought to sacrifice all that is dear for its success and continuation," he said.
The sitting began with readings from the Koran and many tributes to the minister who died, Mohammed Awadh from one of the Sunni factions.
Among those attending the session were the interior minister, whose officials have now taken over security at the parliament building from a private firm.
The BBC's Jim Muir in Baghdad says questions are being asked about how the bomber managed to penetrate one of the most stringently guarded buildings in the country.
The bomber would have had to pass through a checkpoint manned by US and Iraqi forces on the edge of the Green Zone and then through several inner checkpoints run by security contractors.
One MP questioned the parliament's checks, telling the BBC's World Today programme that some MPs' bodyguards were allowed to pass through checkpoints without being searched.
Footage showed officials carrying the injured from the building
One report says police are questioning three workers from the cafeteria where the bomb went off.
A senior Iraqi lawmaker told Reuters news agency that no charges had been filed, adding that some parliamentary guards were also helping police with their investigation.
This is the first time a bomb has gone off inside the parliament building although it has been shaken by several mortar attacks in the past.
The attack is a major blow to the much-trumpeted Baghdad security surge now in its third month, our correspondent says.
The security drive has brought down the rate of sectarian murders, but it has not stopped the bomb attacks.
Iraqi Prime Minister Nouri Maliki said the attack was a "criminal cowardly act" and that the violence would not weaken MPs' resolve.
US President George W Bush condemned the attack and said the US would help Iraq defend itself against extremists.
"It reminds us, though, that there is an enemy willing to bomb innocent people and a symbol of democracy," President Bush said.
The US government has denied that the attack shows its troop increase in the capital is having little impact on security.