MOSUL, Iraq — The death toll from a car bombing south of Baghdad claimed by the Islamic State group rose to 73 on Friday, including about 40 Iranian pilgrims, as Iraqi forces continued to inch closer to the center of the northern city of Mosul in street-to-street fighting east of the Tigris River.

Iraqi police and hospital officials said 65 other people were wounded in the Thursday night attack at a gas station on a major highway near the city of Hilla, about 95 kilometers (60 miles) south of the Iraqi capital.

It was the deadliest IS attack in Iraq since July, when a car bomb killed about 300 in a commercial district in Baghdad.

IS claimed the attack in a brief statement on its Aamaq media arm, saying it was a suicide truck bomb. Earlier, Iraqi officials, who spoke on condition of anonymity because they were not authorized to talk to the media, had put the death toll at 56.

The attack appears to have targeted a bus with Iranian pilgrims heading home after a major Shiite religious observance in the holy city of Karbala.