More than 30 people have been killed and scores injured in suicide bombings in northern Iraq.
The US says violence has been falling as Iraqis confront al-Qaeda
A car bomber killed more than 20 people when he was stopped by police and local militias in Baiji, about 250km (155 miles) north of Baghdad.
The Iraqi Interior Ministry sacked the Baiji police chief after the attack.
Later, a suicide bomber killed 10 people in Baquba, at the funeral of a father and son who were part of a Sunni group allied to US forces.
A number of Sunni tribal militias have turned against al-Qaeda.
They are credited with pushing back al-Qaeda in areas where they had been operating with relative freedom.
Membership around 80,000
Sunnis and former insurgents
Paid by the US
US officials say this has helped reduce attacks in Iraq by 60% since June.
But neighbourhood patrols have increasingly come under attack from Sunni radicals.
In Baiji, the bomb hit people queuing to buy gas cylinders in a residential area. Women and children were reported to be among those killed.
Witnesses said the attack there targeted a security checkpoint on a road leading to a residential compound housing employees of the Northern Oil Company.
The Iraqi Interior Minister Jawad al-Bolani ordered the dismissal and interrogation of the Baiji police chief shortly after the attack.
Baiji, a mostly Sunni area in Salahuddin province, has been relatively quiet in the past two years and the presence of the militias could explain why it is being targeted once more by suicide bombers, says the BBC's Jo Floto in Baghdad.
At least 19 people were killed and dozens wounded in two car bomb attacks there in October.
The suicide blasts targeted the town's police chief and a tribal leader, Thamer Ibrahim Atallah, a senior member of the Salahuddin Awakening Council.
In Tuesday's attack at the funeral in Baquba, the capital of the restive Diyala province 60km (35 miles) north of Baghdad, the bomber, wearing a vest packed with explosives, also wounded 21 members of the local militia, police said.
Police said the father and son who were being buried had mistakenly been killed by US troops.
The US military has only said its troops killed two "armed individuals".