At least 48 people have been killed in Baghdad in the third blast in the Iraqi capital in three days, security and medical sources say.
A car packed with explosives blew up near car dealerships in the Shia area of Bayaa in the south of the city. More than 50 people were injured.
The Islamic State (IS) group claimed the attack, saying it targeted "a gathering of Shias".
At least 24 people were killed in other attacks on Tuesday and Wednesday.
Baghdad saw a wave of deadly suicide attacks by IS in the first few days of 2017, but the number had dropped until recently.
An AFP reporter at the scene of Thursday's bomb reported seeing numerous burnt-out vehicles, and blood on the ground.
Security sources said the bomb was detonated in a busy street and was the deadliest attack in Baghdad for several months. A plume of smoke from the blast could be seen above the Bayaa neighbourhood for much of the day.
Medics have warned the number of fatalities and injuries could rise as they struggle to cope with scores of people wounded in the attack.
It is thought that car dealerships may present convenient targets for the militants because it is easy for them to leave vehicles laden with explosives alongside lots of other vehicles that are also parked in the same area.
As the clear-up operation gets underway, distressed relatives are reported to be at the scene desperate to find news of their loved ones.
The IS group has stepped up its attacks since the Iraqi army, aided by US-led coalition strikes, launched its campaign to dislodge the Sunni militant group from its stronghold of Mosul in the north four months ago.
The militants now control the west of the city, while the eastern part is held by Iraqi forces and their allies.
On Wednesday, an attack on used-car dealers in the Habibya area of Sadr City, a suburb in the north of the Iraqi capital, left 18 dead.
On Tuesday, a car bomb in the south of Baghdad killed four people.
On 2 January, at least 35 people were killed in a bomb blast in Sadr City, in an attack claimed by IS.