A car bomb in the Iraqi capital Baghdad killed at least 27 people and wounded more than 45 in a mainly Shia district in the city's south, police and medical sources said.
The blast occurred on a busy commercial street in the Amil neighbourhood.
Daesh said it carried out the attack. The group has increased its attacks in the capital since the Iraqi army's assault on Mosul began.
Federal Police and Rapid Response units backed by helicopter gunships pressed their cautious advance on the al-Nuri Mosque in western Mosul's Old City on Monday.
The battle for Iraq's second city is expected to last several more weeks. The offensive was launched in October with support from US artillery, air strikes and advisers, and the eastern side of the city on the Tigris river was secured in December.
The campaign for the western side is harder. The area is more densely populated, the streets are narrower and the houses closely packed together.
Daesh fighters captured an Iraqi police colonel and eight other officers on Monday after they ran out of ammunition during a skirmish in the battle for western Mosul, an Iraqi Interior Ministry official said.
The official, who declined to be identified, said the incident took place as government forces closed in on Daesh fighters in the Old City and other districts, in an offensive intended to crush the hardline group.
A media officer for the Interior Ministry's Rapid Response units, Lieutenant Colonel Abdel Amir al-Mohammedawi, denied that any police officers had been captured when asked for comment.
But the Interior Ministry official told Reuters the nine men were seized in the early hours of Monday in Bab Jadid district. Their exact whereabouts were not known, nor their fate.