Three strong blasts reverberated through the city at about 01:35 (20:45 GMT). The cause of the blasts was unknown but it appeared the explosions occurred on the western side of the Tigris river where the US-controlled Green Zone is located.
A fourth, smaller blast occurred a few minutes after the initial volley.
Despite the early handover of power to a transitional Iraqi authority, violence has continued unabated across the war-ravaged country.
A British occupation soldier was killed on Monday and two others were wounded when their convoy passed over a landmine fashioned as an improvised explosive device in the southern city of Basra, British military officials said.
Upsurge in violence
In Ramadi, clashes erupted between resistance fighters and US occupation forces just hours after the handover was announced.
The fighting left one Iraqi dead and two others hospitalised in critical condition.
A doctor at Ramadi Hospital said one Iraqi was killed and eight were wounded in the crossfire.
The hospital was chaotic on Monday - one corpse lay under a blanket, while several wounded people received treatment.
Also, two Iraqis were killed and another wounded in a bomb attack targeting a US military convoy near the Iraqi city of Baquba, 60km north of Baghdad, the city hospital said.
Attacks on British soldiers in
southern Iraq have been rare
"Two Iraqis were killed in an explosion which hit their utility vehicle and a third person, on another vehicle, was injured," said hospital official Muhammad Jafar.
The explosion occurred at about 09:00 (05:00 GMT) in the Hadid area to the city's northeast, Jafar said.
"In a separate incident, eight Iraqis were injured when two mortar rounds hit Anbaar University and a ceramic factory west of the city," an Aljazeera correspondent reported.
"The source of the rounds, which caused some material damages, has not been identified", he added.
Transfer is 'Deceit'
Meanwhile, the Association of Muslim Scholars (AMS) said the transfer of power to the Iraqis was a "nominal development". In a statement sent to Aljazeera, the AMS described the handover as "a deceit to the Iraqis and to the world". It also stressed that US-led occupation troops should withdraw from Iraq.
The AMS went on to say that if the handover required the withdrawal of occupation forces, then "today would have been considered a holiday for all Iraqis."
Abd al-Jabbar: There is still not
a complete sovereignty in Iraq
Meanwhile, in an interview with Aljazeera, Abd al-Sattar Abd al-Jabbar, a member of AMS wished the interim government "good luck."
He also said the interim government should govern Iraqis "fairly and honestly" and "should have complete power over the country, something which it has been deprived of for a long time."
Abd al-Jabbar expressed his concern over the new arrangement and said that "there is still not a complete sovereignty in Iraq."
He concluded by saying that the new government should deal with the Iraqi citizens "as one family and should try to reform its performance."