Three cafeteria workers in Iraq's parliament have been detained for questioning over a deadly suicide bombing at the heavily guarded building the day before, a senior lawmaker said on Friday.
Hasan al-Senaid, from the ruling Shi'ite Alliance bloc, said some parliamentary guards were also being investigated but none were being held.
"The investigations are ongoing inside the parliament. So far three workers from the cafeteria have been detained," Senaid told reporters outside the building, adding that no charges had been filed against the three.
A special parliamentary session to condemn the bombing was called by the speaker of parliament, Mahmoud Mashhadani, for 11 am, but the time passed with no sign of lawmakers gathering.
The US military said eight people were killed and more than 20 wounded on Thursday when the bomber, whose identity is still not known, slipped through multiple checkpoints and blew himself up amid lawmakers having lunch in the cafeteria.
Interior Ministry spokesman Brigadier-General Abdul Kareem Khalaf had a much lower toll, saying only two people had died, a man and a woman, while 23 were wounded. A parliamentary official said the two dead were lawmakers.
It was the worst breach of security in Baghdad's most heavily fortified area -- the Green Zone that houses parliament, government offices, the US embassy and Saddam Hussein's former palaces.
The compound was set up after the US-led invasion of Iraq in 2003.
"There has to be a revision in the security apparatus," Khalaf said.
"Just like the security apparatus make their plans, the criminals make their own plans, and they must have their aides here and there too."
An agency journalist said there was heavier security around the parliament, housed in a former conference centre, on Friday, which is a holiday in Muslim Iraq and a day of prayer. There were more Iraqi police backed up by US troops.
An aide to Mashhadani said he was expected to condemn the blast during the scheduled special session. The attack defied a two-month-old US-Iraqi crackdown in the city that has put tens of thousands of troops on the street to curb sectarian violence between majority Shi'ites and minority Sunni Arabs who were dominant under Saddam.
The operation has succeeded in reducing the number of targeted killings, but US and Iraqi commanders have found car and suicide bombers much harder to stop.
"Those who are implementing the security plan are now faced with a dangerous challenge," said Saleem Abdallah, a lawmaker with the Accordance Front, the biggest Sunni political bloc in parliament.
"If it was possible to reach this (building), then it is possible for them to reach other institutions in the same area."
Iraq's authorities were investigating on Friday how explosives were smuggled into the parliament building.
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 review of security procedures will likely look at the special passes given to some VIPs and their bodyguards that allow them to pass into parliament without being searched.