Violence in Baghdad and north of the capital killed at least 37 people on Monday, the country's bloodiest day in three weeks after Al-Qaeda's front group in Iraq warned it sought to retake territory, AFP reports.
The violence, which also left at least 74 people wounded, came a day after a spate of bombings around the country killed 17 people, shattering a relative calm in recent weeks in the run-up to the holy Muslim fasting month of Ramadan, which began in Iraq on Saturday.
In Monday's deadliest attack, a series of explosions in the town of Taji killed at least 18 people and wounded 29 others, according to two medical officials.
One of the medical officials said the explosions included a suicide attack when emergency responders came to help victims of an initial set of roadside bombs in the town, which lies 25 kilometres (15 miles) north of Baghdad.
Also north of the capital, at 5:00 am (0200 GMT), gunmen launched an assault on a military base in Albu Slaib, east of the town of Dhuluiyah, killing at least seven Iraqi soldiers, according to a medic at the hospital in the nearby town of Balad.
An Iraqi army first lieutenant put the toll at 15 dead and four wounded from the attack. Both spoke on condition of anonymity.
Bombings and shootings also hit Baghdad, as well as Saadiyah, Khan Beni Saad, Kirkuk, Tuz Khurmatu and Dibis, all of which are north of Baghdad.
A series of explosions in Kirkuk city and the eponymous province's towns of Tuz Khurmatu and Dibis killed at least seven people and wounded 29 others.
Gunmen also attacked army and police checkpoints in Saadiyah and Khan Beni Saad, in restive Diyala province, killing two soldiers and a policeman and wounding four other members of the security forces, officials said.
Two other people were killed by a car bomb in the north Baghdad neighbourhood of Husseiniyah, according to security and medical officials.
The attacks came a day after a spate of bombings across Iraq killed at least 17 people and wounded nearly 100 others.
There was no immediate claim of responsibility for the attack, but Al-Qaeda's front group in Iraq has warned in recent days that it seeks to retake territory in the country.