At least 92 people have been killed and 161 wounded in a string of deadly attacks across Iraq, security sources told Al Jazeera, in attacks mostly targeting Shia Muslims, who mark a big religious festival next week.
No one has claimed responsibility for Monday's bombings, but rebel groups frequently target civilians and members of the Iraqi security forces to undermine confidence in the country's Shia-led government and agitate sectarian tensions.
The attacks started in the town of Beiji, 180 kilometres north of Baghdad, where a suicide bomber rammed his explosives-laden vehicle into the main gate of the town police station.
Three other bombers then ran into the station and blew themselves up, killing eight officers and wounding five others, the official 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, adding that all of the bombers were killed before reaching the building where the detainees are held.
Reuters news agency, citing police and and medical sources, reported later on Monday that two parked cars laden with explosives and a roadside bomb went off near a funeral tent and killed at least 24 Shia Muslim pilgrims in Yusfiya, 20 kms south of Baghdad.
Another attack occurred in Baghdad's southeastern neighbourhood of Bayaa when a car bomb went off in a parking lot, killing six civilians and wounding 12 others.
Security services have been on high alert since last week because they expected attacks on Shia pilgrims before Iraq's majority community marks the ritual of Arbaeen, commemorating the death of Imam Hussein.
Car bombs also went off in the central Salhia neighbourhood, where several foreign and key government offices are located, an outdoor market in Baghdad's central Sadriyah neighbourhood, a bus station in the al-Nahda area, the Hussainiyah suburb, the southeastern suburb of Jisr Diyala and the city council building in the northern city of Tikrit.
Monday's bombings are part of a wave of violence that has swept over Iraq since a security crackdown on a protest camp in a northern Sunni town in April.
In addition to Monday's bombings, gunmen opened fire on a bus in Mosul that was carrying Shia Muslims travelling to the shrine city of Karbala.
At least 262 people have died in attacks across the country this month, according to the AP news agency, making 2014 the most violent year in Iraq since the country was pushed to the brink of civil war in 2006 to 2007.