Baghdad: At least seven mosques and dozens of shops in eastern Iraq were firebombed on Tuesday, security sources and local officials said, a day after 23 people were killed there in two blasts claimed by IS.
Ten people were also shot and killed in Muqdadiya, 80 km (50 miles) northeast of Baghdad, security and hospital sources said.
The rise of the militant group IS has exacerbated a long-running sectarian conflict in the country.
A surge in such violence could undermine efforts by Prime Minister Haider Al Abadi to dislodge the militants from large swaths of the north and west that they seized in 2014.
At least two mosques south of Baghdad were attacked last week.
At the height of Iraq's civil war nearly a decade ago, such mosque attacks often unleashed revenge killings and counter attacks across the country.
Officials tried on Tuesday to head off further violence, condemning the mosque attacks as well as Monday's bombings.
Abdul Lateef Al Himayim, head of Iraq's government body overseeing religious sites, called them "a desperate attempt to destroy Iraqi unity", while the United Nations warned in a statement the mosque bombings could "take the country back into the dark days of sectarian strife".
Haqqi Al Jabouri, a member of the local council in Diyala province where Muqdadiya is located, said both types of attacks hurt the social fabric of the community. He blamed "undisciplined armed men" for burning the mosques.
Militias were crucial in keeping IS from overrunning Baghdad and southern areas during their lightning advance across the Syrian border in 2014, and have supported Iraqi forces pushing back the militants, including from parts of Diyala.
Militia elements have been accused of human rights abuses, allegations the groups have repeatedly denied or blamed on rogue members.
Amal Omran, a member of the Diyala council, blamed the mosque attacks on "infiltrators" seeking to smear the image of the militias.
Witnesses said some of the those killed on Tuesday had been shot inside their homes or dragged into the street and executed by gunmen wearing black and camouflage uniforms.
Police sources and local residents said the gunmen were patrolling Muqdadiya and warning families through loudspeakers to leave the city or face death.
Reuters could not verify these accounts.
"It's worse than hell. I hid my two sons under a pile of clothes inside a wardrobe to avoid being discovered," said Um Ibrahim, a widow who fled to nearby Khanaqin after seeing two mosques engulfed by black smoke.
The attacks occurred in the central districts of Mualimeen, Asri and Orouba, the security sources said.
Two Iraqi journalists were also killed on Tuesday outside Baquba, Diyala's provincial capital 65km (40 miles) northeast of Baghdad, according to police, a security official and their network Sharqiya TV.
They said the men had been turned back from a checkpoint near Muqdadiya run by a militia. On their way back to Baquba, gunmen sprayed their vehicle with automatic gunfire.
Earlier in the day, a suicide bomber attacked a police convoy near Baquba, critically wounding a senior police officer and killing three other members of the security forces, police said.
Brigadier Qasim Al Anbuki, the local head of police intelligence, was leading a force to check tips about a suspected car bomb parked on a highway linking Baghdad to Baquba.
After reaching the site, a suicide car bomber detonated his vehicle near the officer's convoy, police sources said. Four others were also wounded, they added.
There was no immediate claim of responsibility for the blast.
Abadi condemned a separate attack on Monday at a mall in a district of Baghdad that killed 18 people. He called it "a desperate attempt by terrorist gangs after our forces' victories in Ramadi and other areas".
The Iraqi government last month claimed victory against IS in the western city of Ramadi, and has slowly pushed them back in other areas.