A bomb killed four people in the southern Iraqi city of Basra on Tuesday, the first such attack in years, Reuters reported.
The blast was caused by a motorbike rigged with explosives, the military said in a statement, citing preliminary information.
"The blast carries fingerprints of ISIS," Basra Governor Asaad al-Edani told reporters.
Policemen were collecting body parts from a minibus that was badly damaged by the blast, a Reuters witness said. The street was covered with broken glass and blood. The governor announced three days of mourning.
"Today and after this terrorist act, the people of Basra must definitely be cautious and careful. Basra became unsafe today," said Mohammed Ibrahim, a car mechanic whose workshop was near the blast site.
Police and hospital sources earlier told Reuters that 20 people had been wounded, in addition to the four fatalities.