Insurgent bombers sent a deadly response to a rash of successes by Iraqi security forces on Sunday, when they triggered a series of blasts in a crowded Baghdad market and killed at least 20 civilians.
Earlier, Prime Minister Nuri al-Maliki's government had announced the arrest of a 16-strong gang accused of launching car bomb attacks in the capital and plotting to kill or kidnap members of the premier's own family.
Maliki's security forces and their US allies also stormed the health ministry to seize guards employed there that had been accused of kidnap, and the US-led coalition announced the arrest of a "key terrorist cell leader".
But before the authorities could savour their successes, bombers struck again, demolishing two buildings in a complex string of rocket and bomb attacks in a mixed area of Baghdad populated by Sunnis, Shiites and Christians.
Defence and interior ministry officials said the attack on the Al-Qubyasi market - which killed at least 20 people and wounded 75 others - used almost every weapon in the insurgent's arsenal.
The carnage began when a Katyusha rocket brought down a four-storey building. Then a suicide car bomber set off his explosives as bystanders rushed to rescue those trapped in the rubble, a witness said.
This was followed by two roadside bombs - one of which brought down a second building while the other wounded three police - and a second suicide attack by a man on an explosives-laden motorcycle, security sources said.
A medical official said from the scene that the death toll could rise.