At least 73 people have been killed and some 167 injured in a double suicide bombing near a busy market in the Iraqi town of Hilla, local police have said.
The attacks left dozens injured across Baghdad and in Hilla
A police source told the BBC an officer tried to stop and search the first attacker, but as he did so both men detonated their explosives.
It came as at least 10 other people were killed in bomb and mortar attacks across the capital, Baghdad.
Six people died when a minibus was hit in the mainly Shia area of Karrada.
Three more people died in a car bomb in another mainly Shia district of the capital, Rusfasi.
The blasts followed mortar attacks in the mainly Sunni area of Adhamiya, in which at least one person was killed.
Police said they also found 30 unidentified bodies across the capital.
The bloodiest attack occurred close to a crowded market in the mainly Shia town of Hilla, about 120km (75 miles) south of Baghdad.
The two bombers were on foot and approached a barrier at the entrance to the market, police said.
The barrier had been in place since a massive bombing in the town centre in 2005 that killed more than 120 people.
Police thought one of the men was acting suspiciously and moved to stop and search him.
The bomber detonated his explosives and the second man walking behind him then did the same, according to police.
The BBC's Mike Wooldridge, in Baghdad, says markets have been a particular target of the bombers over the past couple of weeks - mostly in Baghdad but outside the capital too.
Meanwhile, the Iraqi government has denied using excessive force in a battle last weekend in which more than 260 people died near the Shia holy city of Najaf.
A government spokesman said Iraqi and US forces fought members of a religious cult, calling themselves the Soldiers of Heaven, who had threatened to carry out acts of terrorism.
The group had resisted repeated calls to surrender, and as for the level of force used, Ali Dabbagh said the government was entitled to protect Iraqi citizens.
However, the official version of events has not gone unchallenged and controversy is growing.
According to accounts on an Iraqi website and in the British media, the drama began with a clash between an Iraqi tribe on a pilgrimage to Najaf and an Iraqi army checkpoint.
The fighting escalated, army commanders called for reinforcements and US aircraft launched an aerial bombardment - with significant loss of life.
According to this account, the involvement of the Soldiers of Heaven appears to have been accidental.