Sixty bodies have been found scattered across the Iraqi capital Baghdad, police there have said.
Tuesday's bomb follows a deadly attack on a market on Monday
A car bomb has also exploded near a Sunni mosque in a southern district of the city, killing 11 people.
The bomb attack comes a day after 10 people were killed in a car bombing at a market in the capital.
It also coincides with the release of new figures indicating that an estimated 300,000 Iraqis have fled their homes due to sectarian violence.
Attacks have increased between Iraq's majority Shia Muslims and the Sunni minority, who dominated the country until the fall of Saddam Hussein.
The 60 bodies, who were all men, were found in various parts of the city over a 24-hour period, defence and interior ministry officials said on Tuesday.
Many of them had been shot in the head at close range, execution-style.
The victims also had their hands and feet bound and showed signs of torture - hallmarks of death-squad killings, the police said.
Tuesday's bomb was placed under a car near a mosque in the district of Doura, killing 11 bystanders standing outside a bakery, police said.
The bomb - which also injured at least four people - exploded at about 1100 GMT.
The sustained sectarian violence has seen more than 50,000 Sunni and Shiite families - around 300,000 people - flee their homes, according to figures released by Iraqi minister for migration, Dr Abd al-Samad Rahman.
Some fled their homes after receiving direct threats while others simply felt threatened and moved to areas where their own sect predominates and they feel safer.
The flight is continuing, especially in parts of Baghdad and Diyala province, north-east of the capital.