Iraqi Kurds have begun voting in Iraq's Kurdish region and disputed territories in a historic but non-binding vote on whether to support independence from Iraq.
Millions are expected to vote across the three provinces that make up the Kurdish autonomous region, as well as residents in territories claimed by Baghdad and the Kurds.
The vote is being carried out despite mounting regional opposition to the move and the United States has warned the vote will likely destabilize the region amid the fight with the Islamic State group.
The government in Baghdad has also come out strongly against the referendum, demanding on Sunday that all airports and borders crossings in the Kurdish region be handed back to federal government control.
In a televised address on Sunday night, Iraqi Prime Minister Haider al-Abadi said "the referendum is unconstitutional" and that "it threatens Iraq, peaceful coexistence among Iraqis and is a danger to the region".
"We will take measures to safeguard the nation's unity and protect all Iraqis," he added.
Earlier on Sunday, the Kurdish region's president, Masoud Barzani, said during a press conference in Irbil he believed the voting would be peaceful, though he acknowledged that the path to independence would be "risky."
"We are ready to pay any price for our independence," he said.
In a strongly worded statement, Turkey said on Monday that it doesn't recognize the referendum and declared its results would be "null and void."
Turkey's Foreign Ministry accused Kurdish leaders of endangering peace and stability for Iraq and the whole region.
It reiterated Turkey would take all measures to thwart threats to its national security.
Initial results from the poll are expected on Tuesday, with the official results to be announced later in the week.
Iraqi Kurds have long dreamed of independence, which the Kurdish people were denied when colonial powers drew the map of the Middle East after the First World War.
The Kurds form a sizable minority in Turkey, Iran, Syria, and Iraq. In Iraq, they have long been at odds with the Baghdad government over the sharing of oil revenues and the fate of disputed territories like Kirkuk.