Polls have opened in Iraq's Kurdish-run provinces and disputed territories as Iraqi Kurds cast ballots in support for independence from Baghdad in a historic but non-binding vote.

Millions are expected to vote on Monday across the three provinces that make up the Kurdish autonomous region, as well as residents in disputed territories — areas claimed by both Baghdad and the Kurds, including the oil-rich city of Kirkuk.

The vote is being carried out despite mounting regional opposition to the move. The United States has warned the vote will likely destabilize the region amid the fight with the Islamic State group.

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.