Suicide bombers and gunmen killed at least 54 people in Iraq on Monday, medical and police sources said, in attacks mostly targeting Shi'ite Muslims, who mark a big religious festival next week.
Al Qaeda-linked Sunni Muslim militants have intensified attacks on the security forces, civilians and anyone seen as supporting the Shi'ite-led government in Baghdad, tipping Iraq back into its deadliest levels of violence in five years.
In Baiji, 180 km (112 miles) north of Baghdad, four men wearing explosive belts took over a police station after detonating a car bomb parked outside, police sources said.
Two blew themselves up inside the station, killing five policemen. The other two did the same about an hour later as Iraqi special forces counter-attacked, the sources said.
"We believe the attack was aimed at freeing detainees who are being held in the building next door," said Major Salih al-Qaisi, a police officer at the scene.
"All the militants were killed before they reached the police department building where the detainees are held."
No group immediately claimed responsibility for the attack, but suicide bombings are the trademark of al Qaeda's Iraqi wing, which merged this year with its Syrian counterpart to form the Islamic State of Iraq and the Levant (ISIL).
Two hours later, three suicide bombers seized the local council building in Tikrit, 150 km (95 miles) north of the capital, after setting off two car bombs outside, security sources said. At least three people were killed.
Security forces surrounded the building, where the militants were thought to be holding hostages, and imposed a curfew on the city, the sources said.
The Interior Ministry put the toll for the attacks in Baiji and Tikrit at 11 dead, including the suicide bombers, and three wounded.
WAVE OF BOMBINGS
A spate of car bombs and roadside bombs in mainly Shi'ite neighborhoods of Baghdad also killed at least 27 people and wounded scores, police and medical sources said.
In Mosul, 390 km (240 miles) north of Baghdad, militants in a car intercepted a bus carrying Shi'ite pilgrims to the shrine city of Karbala from the northern Shi'ite town of Tal Afar, and shot 12 of them dead, police said.
Security services have been on high alert since last week because they expect more attacks on Shi'ites before Iraq's majority community marks the ritual of Arbaeen, commemorating the death of Imam Hussein, grandson of Prophet Mohammad.
Shi'ites are considered apostates by Sunni militants, whose resurgence is blamed by the government partly on the impact of the increasingly sectarian war in neighboring Syria.
Prime Minister Nouri al-Maliki's critics say his policies have also fuelled Sunni discontent, giving al Qaeda an opportunity to rebuild after its setbacks at the hands of Sunni tribal militias backed by U.S. troops before they left in 2011.
This year has been Iraq's most violent since 2006-7, when tens of thousands died in strife between Sunnis and Shi'ites.
Hundreds of Iraqis were killed last month, figures from the United Nations and the Iraqi government showed.
ISIL has targeted government buildings and security headquarters since the start of the year with apparently coordinated attacks involving suicide bombers on foot, car bombs, rockets and gunfire several times a month.
Earlier this month, gunmen and suicide bombers attacked a police intelligence headquarters and a nearby shopping mall in the northern city of Kirkuk, killing 11 people and wounding 70. ISIL claimed responsibility for that assault.