"Security forces repelled an attack by the terrorist gangs on a police station of al-Mafraq area in western Baquba and killed 52 detainees by hand grenades and mortar shelling," Lieutenant General Qassim Atta, security spokesman of Prime Minister Nuri al- Maliki, told reporters.
Atta also confirmed that the forces have repelled the attackers in western Diyala's provincial capital city of Baquba, some 65 km northeast of Baghdad.
A police source in the province put the number of the killed detainees at 44, saying that the medical reports showed that some of them were killed by bullets, others were suffocated to death by smoke and others by shrapnel.
Most of the killed detainees faced suspected charges of terrorism, and a few of them were held for criminal charges, the source told Xinhua on condition of anonymity.
However, residents in the city held the forces responsible for the killing of detainees, but the authorities denied the accusation, according to the provincial source.
Earlier in the day, Major General Jamil al-Shimary, Diyala's provincial police chief told Xinhua that hundreds of militants, including the militants linked to the Islamic State in Iraq and Levant (ISIL), an al-Qaeda offshoot, attacked the western suburbs of Baquba and clashed fiercely with the troops.
The clashes which erupted late on Monday night and continued to early in the morning left nine militants and two policemen killed, along with wounding six policemen, by the attack on the police station and another military base in al-Mafraq area, al- Shimary said.