At least 90 people have been killed and 265 injured in two car bomb attacks in central Baghdad, Iraqi officials say.
The blasts hit the ministry of justice and a provincial government office near the Green Zone, causing severe damage.
They came in quick succession at 1030 local time (0730 GMT) as people headed to work during the morning rush hour.
Correspondents say these are the largest attacks since 19 August, when truck bombs hit two ministry buildings and killed at least 100 people.
Iraq then blamed foreign fighters and accused Syria of involvement, demanding a UN investigation.
Government spokesman Ali al-Dabbagh said he suspected that al-Qaeda militants or members of Saddam Hussein’s former government were behind the attacks.
“The initial analysis shows that it bears the fingerprints of al-Qaeda and the Baathists,” Mr Dabbagh said in a statement after being caught in a nearby hotel, where he saw others around him being showered in shattered glass.
Plumes of smoke were seen rising in Baghdad on Sunday morning after two vehicles packed with explosives blew up just outside the Green Zone, the heavily-fortified administrative heart of the capital.
There were conflicting reports from Iraqi police and other security officials about whether suicide bombers were involved.
Search for survivors
Iraqi officials say the number of dead and wounded is likely to rise, as rescue workers dig through the rubble to search for survivors.
“The walls collapsed and we had to run out,” Yasmeen Afdhal, a 24-year-old employee at the Baghdad Governorate told AP news agency.
“I don’t know how I’m still alive,” local shop owner, Hamid Saadi, told Reuters by telephone from near the justice ministry. “The explosion destroyed everything … it’s like it was an earthquake, nothing is still in its place.”
The BBC’s Gabriel Gatehouse in Baghdad said he felt the force of the explosions this morning, even though he was several miles away.
Our correspondent says it is too early to determine who is behind the attacks.
But he says the finger of blame is likely to point to insurgents or foreign fighters trying to destabilise the security situation ahead of Iraqi elections in mid-January.
Overall, violence has dropped dramatically in Iraq compared to a year ago, but sporadic attacks still continue in several parts of the country.