Iraq’s semi-autonomous Kurdistan Region is holding an independence referendum despite widespread criticism from the Iraqi government and calls from the international community to cancel the vote.

A total of 12,072 polling stations opened on Monday at 8:00 local time. More than 5.3 million are eligible to vote in the referendum which will last for 12 hours.

The polling stations are located across the three provinces of Erbil, Sulaimaniyah and Dohuk that form the Iraqi Kurdistan retgion as well as in disputed bordering zones such as the oil-rich province of Kirkuk.

The referendum has been called illegal by the central government.

On Sunday, Baghdad urged the world countries not to purchase oil from Kurdistan Region in response to the vote, hours after Prime Minister Haider al-Abadi vowed to take “necessary measures” to protect Iraq’s unity.

Regional countries, including Iran, Turkey and Syria have denounced the independence vote, underlining the importance of maintaining the territorial integrity and stability of Iraq.

A day prior to the vote, Iran closed its airspace to all flights to and from the Kurdish region at the request of the Iraqi central government.

Turkey has also warned that the disintegration of Iraq has the potential to turn into a major global conflict.