A suicide bomber detonated on Monday morning an explosives-rigged vehicle killing 16 people including a group of women and children packed into a minibus outside an Iraqi town in the eastern province of Diyala, police and hospital sources said.

The blast also wounded 37 people, according to Colonel Ghalib Al Attiyah, the Diyala province police spokesman, and health department spokesman Faris Al Azzawi.

ISIS terrorist group claimed the attack. Amaq, a news agency that supports ISIS, said the attack had targeted Iraqi troops in Khalis, which is located in the eastern province of Diyala, a mixed Sunni-Shi’ite Muslim area bordering Iran.

A police officer at the scene said most of the victims died inside their vehicles while waiting at a checkpoint to enter Khalis, about 80 km (50 miles) north of Baghdad.

“We still have charred bodies inside many vehicles including a minibus packed with women and children,” the police captain said, requesting anonymity.

The blast came a day after a suicide bombing claimed by ISIS killed at least 15 people in Baghdad’s Kadhimiyah neighborhood.

Iraq declared victory over insurgents in Diyala more than a year ago, but the militants remain active despite holding no significant territory there. ISIS has stepped up attacks across the country even as it incurs battlefield setbacks in the country’s north and west. Experts have warned there may be more such attacks as it continues to lose ground.

Iraqi Prime Minister Haider al-Abadi has come under renewed pressure to improve security since a suicide attack claimed by ISIS earlier this month killed 292 people in central Baghdad, one of the largest attacks of its kind since the U.S.-led invasion in 2003.

The ultra-hardline militants have lost much of the territory they seized in 2014 and Iraqi forces are conducting operations to set the stage for the battle to recapture Mosul, the last ISIS-held city in the country.