At least 30 people were killed and over 63 others injured in a suicide attack carried out Monday in al-Muqdadiyeh city in Diyala province, north-east of the Iraqi capital Baghdad, medical and security sources said.
A suicide bomber wearing an explosive belt blew himself up at a funeral attended by members of the Popular Mobilization Forces - a paramilitary group known for fighting Sunni extremist organization Islamic State - the sources said.
The number of casualties is expected to rise due to the severity of the injuries, the sources added.
Islamic State claimed responsibility for the attack.
There have been repeated reports of abuses by pro-government Shiite militias in Diyala, a religiously mixed province, since the Sunni extremist Islamic State captured large areas of northern Iraq in mid-2014.
Last year Human Rights Watch said that 3,000 people had fled al-Muqdadiyeh, located north-east of Baquba, the capital of Diyala, and been prevented from returning. The group also reported abductions and executions of Sunni civilians.
Meanwhile, the death toll from Sunday's suicide bombing in an eastern Baghdad market reached more than 70, the Iraqi Health Ministry said.
The ministry said Monday that more than 150 people had been injured in the attack in the Shiite Sadr City district of the capital.
The blast was also claimed by Islamic State.
Prime Minister Haider al-Abadi visited the scene of the attack late Sunday, a statement from his office said.
The premier vowed that what he called "cowardly criminal acts" would not deter the government from "continuing our victories and crushing these gangs."
Sunday also saw Islamic State attacks on security forces in several parts of the country.