Parts of Kirkuk were described as a "ghost city" on Monday as thousands of residents were either in hiding or had fled in fears of clashes after Iraqi military forces launched an operation against Kurdish fighters.
The military operation is rooted in a long-standing territory dispute. The city, home to Iraqi Arabs, Turkmen, Christians and Kurds, emerged as a flashpoint in the crisis between Baghdad and Erbil, the capital of the autonomous Kurdish region, as it is claimed by both sides.
The city has been held by Kurdish forces who recaptured it from ISIL in 2014 and was included in Iraqi Kurdistan's independence vote last month even though it is not part of the Kurdish region.
Thousands of residents were seen fleeing the city as shops, businesses and schools were shut on Monday.
"We're leaving because we're scared there will be clashes" in the ethnically mixed city of 850,000 people, said 51-year-old Chounem Qader.
As local crowds on the streets of Kirkuk's southern outskirts welcomed Iraqi forces, an official in charge of displaced individuals said "tens of thousands, mostly Kurds, were heading out of the city".
Omar Dawood, 34 years old, mechanical engineer living in the city, said: "I saw hundreds of people fleeing the city, mostly Kurds, they are going north towards Erbil- the capital of Iraqi Kurdistan," Mr Dawood told The National.
"People in Kirkuk were relieved to hear that Iraqi forces have entered the city, I saw the Iraqi flag being raised," he said.
Mr Dawood raised concern that those who remain in Kirkuk "fear that the Kurds might seek to retaliate, we are all scared and tense."
Iraqi forces seized a key military base, an airport and an oil field from Kurdish fighters in disputed Kirkuk province in a major operation launched on Sunday night. By Monday evening they controlled the city centre.
Soha Ahmad, a 28-year old housewife living in a residential area in Kirkuk told The National that constant gun shots and explosions were heard since early morning.
"We have been in doors the whole day, my family and I are so afraid of leaving our house," Mrs Ahamd said.
"Schools and businesses are closed, I didn't send my kids to school my husband didn't go to work, everything is shut. We are afraid of what is to come.”
Himen Chouani, a 65-year-old Kurd pinned the blame on politicians in both Baghdad and Erbil.
"We were living in peace but politicians don't want good things for us, neither in Baghdad nor Erbil. They're fighting to control the oil, and the victims are us, the residents of Kirkuk," he said.
Rula Ayoub, an English teacher living in Kirkuk told The National that the Peshmerga's intelligence office is opposite to her house.
"We couldn't sleep all night, we saw the employees getting in to cars this morning, the officials fled as soon as reports came in that Iraqi troops were heading towards the centre of the city," Mrs Ayoub said.
The ethnically mixed city of Kirkuk is claimed by both the Kurds and Baghdad's central government.
Kurdish forces took control of the province and other disputed areas in the summer of 2014, when ISIL swept across northern and central Iraq and the Iraqi armed forces crumbled.
The move infuriated the Turkmen and Arabs of Kirkuk as the success of the Kurdish forces in keeping ISIL out also gave the Kurds the upper hand in local politics.
The city participated in Iraqi Kurdistan's independence vote — even though it is not part of the Kurdistan region. The move sparked tensions between Kirkuk’s different ethnic leaders and angered the authorities in Baghdad and Erbil.
In response, the Iraqi parliament asked prime minister Haider Al Abadi to deploy troops to Kirkuk after the referendum results were announced.
Fanar Haddad, senior research fellow at the National University of Singapore, said "the current crisis goes beyond the immediate triggers and events of the last few weeks."
Mr Haddad outlined in "Iraq, Kuridstan and Kirkuk: untying the knot" publication that the crisis "is about the extent of Iraq’s writ and the nature of the relationship between Baghdad and Erbil, Arabs and Kurds."