At least 26 people have died in two blasts in Iraq's Diyala province. One attack was carried out by a female suicide bomber.
Diyala province has been at the centre of recent clashes
Both attackers struck members of US-backed local groups that have been helping to fight al-Qaeda.
A woman wearing a vest packed with explosives killed 16 people in Muqdadiya, 90km (55 miles) north-east of Iraq's capital, early on Friday.
The second blast - a suicide car bombing at a checkpoint - left 10 dead.
Seven of the dead were Iraqi soldiers and three were members of a local anti-al-Qaeda group, Iraqi officials said. Eight people were injured.
The driver detonated his explosives when guards asked to search the car, an official told the Associated Press news agency.
The bombings reportedly happened just 15 kilometres (10 miles) north of the provincial capital of Baquba.
Police say the bomber in the first attack was a local woman who was once a member of executed Iraqi President Saddam Hussein's Baath Party.
She struck at the office of a local Sunni Arab anti-al-Qaeda militia, killing 10 members of the group.
She was targeting one of the so-called Awakening Councils, militias that have backed US forces and the Iraqi government in their efforts to reclaim Iraqi provinces from al-Qaeda.
At least 20 people were wounded in the blast at 0930 local time (0630 GMT).
A female suicide bomber previously struck at Muqdadiya in April this year, walking into a crowd at a police recruitment centre and killing more than a dozen people.
Last month, another female suicide bomb attack in Baquba wounded seven US troops and five Iraqi civilians.
The BBC's Crispin Thorold in Baghdad says Diyala has been the focus of some of the fiercest clashes in Iraq in recent months.
Insurgents displaced from their former strongholds in Anbar province and parts of Baghdad are now thought to be in Diyala, says our correspondent.
Recent months have seen a sharp and sustained drop in all forms of violence in most parts of Iraq, analysts say.
The US troop surge of 30,000 extra troops in and around Baghdad, which started in February, has been credited with this.
But senior US commanders in Iraq have warned recent gains could be fragile.
Also on Friday, the US military in Iraq said 55 suspected militants had been detained in two raids targeting the al-Qaeda in Iraq network north of Baghdad.
It said 47 people were held in a raid by Iraqi forces on the village of al-Aswad on Thursday. Two bombs were found during a search of the village.
A further eight suspects were detained by US and Iraqi forces near Balad. The raid targeted an alleged al-Qaeda in Iraq cell leader, who was killed in the operation.
In Baghdad, US troops have detained nine people suspected of links with al-Qaeda in Iraq.