In January Iraqi officials declared victory over the insurgents in Diyala province, after security and voluntary forces drove them out of towns and villages there. But the terrorists have remained active.
An explosion at a market in Huwaidar, about 4 km north of the provincial capital of Baquba, killed 51 people and wounded at least 80, police and medical sources said, according to Reuters.
"The attacker managed to pass a checkpoint by lining up with a wedding motorcade and then split off with his explosives-packed vehicle to blow it up in a crowded marketplace," said Diyala police captain Mohammed al-Tamimi.
The ISIL terrorist group, which controls large parts of northern and western Iraq, claimed responsibility for the attack in the province and said the target was "rejectionists", as the group refers to Shiites.
A separate blast to the east of Baquba killed a further seven people and wounded 25. ISIL said it had targeted a checkpoint manned by the army and volunteers of Popular Mobilization Forces.
The attacks took place less than a month after a bombing claimed by ISIL in the nearby town of Khan Bani Saad, which killed more than 100 people and prompted riots by distraught mourners.
Security forces and militia groups are currently focused on routing ISIL from the western province of Anbar, where they have been gearing up for an offensive to retake the region.
Iraq has been facing the growing threat of terrorism, mainly posed by the ISIL terrorist group, which is believed to be supported by the West and some regional Arab countries.