ERBIL, Iraq (Reuters) - Kurdish authorities said their forces, backed by U.S.-led coalition airstrikes, drove Islamic State militants from an 84 square kilometer (32 sq mile) area in northern Iraq over the weekend, widening a buffer around the oil-rich city of Kirkuk.
The Kurdistan region's security council said in a statement at least 35 insurgents had been killed by its peshmerga forces in the offensive south of Kirkuk, which began on Saturday on two fronts.
The peshmerga have emerged as a key partner for the United States in its campaign against Islamic State. They have rolled it back in northern Iraq, significantly expanding the formal boundary of their autonomous region in the process.
The Kurds took full control of Kirkuk last summer as Islamic State overran the north of the country, and several divisions of the Iraqi army disintegrated. Kurdish leaders say they will never give up the ethnically mixed city, to which they, as well as Turkmen and Arabs, lay claim.
The U.S.-led coalition said in a statement on Sunday it had provided "reconnaissance (and) advise and assist elements" as well as airstrikes in support of the peshmerga, who had gained "dozens of square miles".
Islamic State deployed one suicide car bomb, the Kurdish security council said, and teams were now working to clear the area of mines and booby traps -- the single highest cause of casualties among the peshmerga.
Last month, the peshmerga pushed the militants out of more than 100 sq km south and west of Kirkuk.
"Peshmerga forces continue to have the initiative - advancing deep into ISIS territory and forcing the group to resort to cowardly acts designed to hurt innocent civilians," the security council statement said, using another acronym for Islamic State.
Reporting by Isabel Coles; Editing by Mark Trevelyan