At least 19 people have been killed in Iraq in bomb attacks targeting police and Shia pilgrims commemorating the festival of Ashoura, according to police and medical sources.
No group immediately claimed responsibility for Wednesday's attacks, which coincided with the holy ritual when Shia Muslims commemorate the prophet's grandson, Hussein, who died more than 1,000 years ago. The 10-day ritual, considered a melancholy event by Shias, ends on Thursday.
The AFP news agency reported 23 deaths. Reuters put the figure at 19, citing its own sources.
Security personnel are also a prime target for Sunni Islamist fighters linked with Al-Qaeda, which seeks to destabilize Iraq's Shia-led government and foment intercommunal conflict.
In the deadliest attack, 10 people were killed when a suicide bomber drove a truck packed with explosives into a police checkpoint in Al-Alam, a town near Tikrit, police said.
Anti-government fighters, many of them linked to Al-Qaeda's Iraqi affiliate, have gained a foothold in Tikrit.
Near the city of Baquba, three roadside bombs exploded near a group of Shia pilgrims commemorating Ashoura, killing nine, medics and police sources said.
The civil war in neighboring Syria has drawn Sunni Islamists from across the region and beyond into battle against President Bashar al-Assad, who is an ally of Shia-led Iran.
Al-Qaeda in Iraq earlier this year joined forces with its Syrian counterpart to form the Islamic State in Iraq and the Levant, which has claimed responsibility for attacks on both sides of the border.
Violence began to ease after Al-Qaeda in Iraq was forced underground in 2007, but it is rising again, with more than 7,500 civilians killed so far this year, according to the monitoring group Iraq Body Count.
In past years, Shia pilgrims have been targeted by bombings, including serial attacks the day before Ashoura in 2011 that killed 28 people.
As a result, security measures are stepped up, with more than 35,000 soldiers and policemen currently deployed to Karbala — the city where Hussein was killed in 680 and a pilgrimage site for Shias — with concentric security perimeters barring vehicles from entering the city while helicopters hover overhead.
Al Jazeera with wire services