The Iranian foreign ministry said the recent move by the Kurdistan Regional Government (KRG) to raise its flag alongside the Iraqi national flag at government buildings is "concerning."
Iranian foreign ministry spokesman Behram Kasimi said "raising any flag apart from the Iraqi national one is against the Iraqi constitution and might rise tension in the country" in a statement released Monday on the ministry's website.
The statement reiterated Iran's respect for Iraq's territorial integrity and national sovereignty, calling all parties in Iraq to abide by the constitution and solve disagreements in a legal framework.
"The most important issue of Iraq and its people is the fight against Daesh. It is concerning to see that the recent move in Kirkuk is drawing attention away from the ongoing fight against the terrorist group," the statement said.
Last week, 26 Kurdish members of Kirkuk's provincial assembly voted in favor of raising the KRG flag alongside Iraq's national flag outside of the city's public buildings and institutions.
But on Saturday, the Iraqi parliament rejected the decision and voted in favor of flying only the Iraqi flag in Kirkuk.
Kirkuk governor Najmiddin Karim, however, refused to apply the parliament's decision to pull down the KRG flag.
The Kirkuk council is also set to meet on Tuesday to discuss holding a referendum on the city's future.
During the 2003 U.S.-led invasion of Iraq, Kurdish Peshmerga forces seized Kirkuk, prompting an influx of Kurds into the city.
Baghdad says Kirkuk is administratively dependent on Iraq's central government, while the Patriotic Union of Kurdistan party demands Kirkuk's incorporation into the Kurdish Region.
Kirkuk's population is mainly composed of Arab, Turkmen and Kurdish inhabitants.