Three car bombs struck the sprawling Sadr City slum in the north of the city, car bombs exploded in Ameen, al-Husseiniyah and Kamaliyah in the east, and a roadside bomb blew up in Karrada in central Baghdad, security and medics said.
Another roadside device went off in Saidiyah in the capital's south.
At least 21 people were killed and more than 120 were wounded in the attacks, the officials said.
Residents of Sadr City were enraged by the bombings, and hospitals in the area were quickly crowded with people searching for relatives, an AFP journalist reported.
The carnage could have been even worse -- the AFP journalist saw soldiers apparently working to defuse another car bomb in the area.
The Baghdad Operations Command, which is responsible for security in the capital, said in a statement that security forces defused a total of six car bombs, including three in Sadr City.
Heavy security measures were put in place after the Sadr City attacks, with some areas closed off.
Security forces also searched cars at the main entrance to Sadr City and helicopters overflew the area, another AFP journalist said.
Also on Sunday, gunmen killed a police captain in front of his home in Mosul in north Iraq, security and medical officials said.
Sunday's attacks bring the number of people killed in violence this month to at least 157, according to an AFP tally based on reports from security and medical officials nationwide.
No group has yet claimed responsibility for the latest wave of attacks.
But Sunni militants linked to the al-Qaeda franchise in Iraq often target the Shiite majority in a bid to erode confidence in the central government and push the country back towards the bloody sectarian conflict of 2006-2007.
The Baghdad bombings follow multiple attacks on Saturday that killed five people, including the head of Iraq's intelligence academy.
Two suicide bombers killed Brigadier General Aouni Ali and two of his guards, and more bombings resulted in the deaths of a judge and an army lieutenant.
Members of the security forces and judicial officials are also often targeted by militants in Iraq.
The latest violence comes after nearly two months of anti-government protests centered on Sunni-majority areas in north and west Iraq, calling for the ouster of Iraqi Prime Minister Nuri al-Maliki, a Shiite, and amid a festering political crisis.
The demonstrations were initially sparked in December by the arrest of several guards of Finance Minister Rafe al-Essawi, a leading Sunni.
The longest-running protests have blocked a key trade route linking Baghdad to both Jordan and Syria.
As the demonstrations have since expanded markedly, the government has sought to curtail them by saying it has released thousands of detainees and raised the salaries of Sunni militiamen battling al-Qaeda extremists.
It has also restricted movements in major cities on Fridays, when the largest protests are staged.
Maliki, meanwhile, has been tussling with a political crisis that has pitted him against many of his government partners barely two months before provincial elections, the country's first since March 2010 parliamentary polls.