Dozens of militants targeted four police stations and Kurdish security offices in Kirkuk, spreading themselves out through neighborhoods.
Security forces killed at least seven ISIS militants in Kirkuk, officials there said, but there was no information yet on civilian casualties. Images broadcast on local television showed what appeared to be dead or injured fighters on the street.
Nearly 30 ISIS militants took over an unoccupied building in Domiz district in southern Kirkuk and started firing on security forces there, according to security officials. Iraqi security forces are surrounding the building now, and sporadic clashes continue.
The situation remains tense in the city, with at least two ISIS bombers hiding inside two buildings in southern Kirkuk, security officials said. Security forces surrounded both locations.
Local authorities imposed a curfew in Kirkuk.
The media wing of ISIS, Amaq, said online that ISIS fighters had attacked Kirkuk before dawn and taken control of 10 neighborhoods as well as carried out attacks to the north and south of the city.
Previous attacks by ISIS militants on Kirkuk have been attempts either to capture the city from the Peshmerga, as the Kurdish fighters are known, or divert Kurdish troops from the fight in Mosul.
In a separate incident, ISIS militants also attacked a government building in Dibis, about 40 kilometers (25 miles) northwest of Kirkuk.
Twelve people were killed, including nine Iraqi employees and three Iranian contractors, two security officials told CNN.