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 told Xinhua.

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 neighborhood 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.

The 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 curfew and blocked the entrances of 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 Islamic State (IS) 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-IS international coalition are carrying out a major offensive to drive out the IS militants from its last major stronghold in and around Mosul.

Many blame the current chronic instability, cycle of violence, and the emergence of extremist groups, such as the IS, on the U.S., which invaded and occupied Iraq in March 2003.

source: Xinhua