Militants detonated a car bomb at the Tikrit city council headquarters on Monday and occupied the building with employees inside, as violence across Iraq left 24 people dead, officials said.
Violence in Iraq has reached a level not seen since 2008, when the country was emerging from a period of brutal sectarian killings, raising fears it is slipping back into all-out conflict.
Security forces from both the army and police deployed around the city council building in Tikrit, near the village of late dictator Saddam Hussein north of Baghdad, an AFP journalist said.
Casualties from the attack were not immediately clear, nor was the number of council employees who were still inside the building, police said.
Security forces also ordered all government employees in the city, including teachers, to go home for the day.
The attack came after suicide bombers attacked a police station in the town of Baiji, which like Tikrit is located in Salaheddin province.
One bomber detonated a car bomb at the gate of the station, after which three entered, shot dead an officer and a policeman, and waited at the station.
SWAT forces then attacked, killing one of the militants, while the other two blew themselves up, killing three police.
And gunmen killed three soldiers guarding an oil pipeline in Tikrit.
Also on Monday, four car bombs and a magnetic “sticky bomb” on a vehicle exploded in and around the Iraqi capital, killing at least 15 people and wounding at least 38 — the second series of blasts in the area in 24 hours.
In one of the deadliest attacks, a car bomb exploded in a car park near the Baghdad provincial council headquarters, killing at least four people and wounding at least 11.
The attacks came after another series of bombings in and around Baghdad killed at least nine people on Monday night.
And violence elsewhere in the country on Monday killed a further 11 people, among them a TV presenter and a family of five.
The presenter, Nawras Al Nuaimi, was the sixth journalist to be killed in Iraq since October, five of whom died in the northern city of Mosul.
More people died in the first eight days of this month than in the whole of last December, and over 6,450 people have been killed since the beginning of 2013, according to AFP figures based on security and medical sources.
Officials have blamed the violence on Al Qaeda-linked militants emboldened by the civil war in neighbouring Syria, but analysts and diplomats also say the government has not done enough to address underlying domestic grievances fuelling the violence.
But daily attacks show no signs of abating.
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