TIKRIT, Iraq,Four suicide bombers, on Monday, attacked two police stations in the city of Samarra, in Iraq's northern central province of Salahudin, leaving at least two police officers killed, a provincial security source said.

The attacks occurred in the evening, when two suicide bombers stormed the al-Imam police station, and two others attacked the al-Mutawakil police station, both located in al-Mu'tasim neighbourhood, in the city of Samarra, some 120 km north of the Iraqi capital of Baghdad, the source from Salahudin provincial police said, on condition of anonymity.

After heavy fire exchange and massive explosions, the police forces, backed by helicopter gunships, managed to retake control of the two police stations, after killing the four attackers, the source said.

There is no immediate report about the exact casualties, but initial reports said that two police officers were killed by the attacks, the source added.

Authorities of the city immediately imposed a curfew and blocked the entrances to the city, as reinforcement troops arrived to deploy in the main streets and around the nearby holy Shiite shrine of Imam Hassan al-Askari, in central Samarra.

No group has so far claimed responsibility for the attack, but the Daesh militant group, in most cases, is responsible for such suicide bombings, targeting Iraqi security forces, as well as, crowded areas, including markets, cafes and mosques across the country.

The attacks came, as the Iraqi security forces, backed by anti-Daesh international coalition, are carrying out a major offensive, to drive out the militants from its last major stronghold in and around Mosul.