At least three policemen were killed in Tuesday's attack, while 25 policemen and eight civilians were wounded, including the deputy head of the city council, Ammar Ahmed, said Omar al-Obeidi, a doctor at Samarra hospital.
Two fighters, possibly wearing explosives-rigged vests or belts, seized the city council building with an unknown number of employees inside, security officials said.
Clashes broke out between the fighters and security forces, and a suicide bomber detonated an explosives-rigged vehicle near police and militia forces when they arrived at the scene.
The attack in Samarra follows a similar incident in Tikrit, another city in the central Salaheddin province, where fighters detonated a car bomb and seized the city council headquarters on December 16.
Security forces ultimately freed the Tikrit hostages, but a city council member and two police were killed.
Violence in Iraq has reached a level not seen since 2008, when the country was just emerging from a brutal period of deadly violence in which tens of thousands died.
More than 1,750 people have been killed in attacks and clashes in Iraq since January 1, according to AFP figures based on security and medical sources.
SHI/SHI