The president of Iraq's semi-autonomous Kurdish region has vowed to go ahead with an independence referendum set for next week despite intense opposition by the Iraqi government and international powers.

The Kurdistan Regional Government (KRG) plans to hold the referendum on support for independence on September 25 in three governorates that make up the region, and in some disputed areas, including the oil-rich province of Kirkuk and parts of the northern province of Nineveh.

"Referendum is no longer in our hands or political parties, it is in the hands of people," KRG head Masoud Barzani said on Friday to thousands of cheering supporters who packed the Franso Hariri Stadium in Erbil, the capital of the Kurdish region.

"The same people who are threatening us have not come to ask why we are holding a referendum," Barzani said, according to a report from Kurdish news portal Rudaw.

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Baghdad is vehemently opposed to the vote, which has also alarmed neighbouring Turkey, which has a large Kurdish minority. Iran and Syria also worry that the vote will encourage secessionist ideas among their own Kurdish minorities.

"We are being pressured day and night to postpone the poll, but we won't repeat the mistakes of the past," Barzani said.

"We are open to holding serious dialogue [with Baghdad] after the poll, but now it's too late to postpone the referendum," he added.

Earlier this week, Turkish President Recep Tayyip Erdogan warned Ankara will consider imposing sanctions on the Kurdish region of northern Iraq over the referendum, and the United States has urged Kurdish leaders to call off the vote, fearing it could inflame regional unrest and distract attention from campaigns to rout the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

After a late-night session by Turkey's National Security Council, Turkey's government called the plans for a vote "illegal and unacceptable."

Should the vote go ahead, Ankara said it would keep "all options" open.

"It is strongly emphasised that this attempt [Kurdish referendum] is a grave mistake which directly threatens the security of Turkey and the peace, security and stability of the region as well as Iraq's territorial unity and territorial integrity," Turkey's National Security Council said in a statement.

But Barzani said he was unbowed.

"If Washington had done to Texas what Baghdad has committed against Kurds, Texas would never go back to Washington," he said.

Barzani accused Baghdad of failing to build a partnership with the semi-autonomous region.

"Since the day Iraq was created, the Kurds have sought partnership time and time again, but they have told us to go to hell!" Barzani said.

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As he was delivering his televised speech, many members of the audience waved the flag of the Kurdish region - red, white and green colours.

Barzani took advantage of the rally to push for a yes-vote for independence.

"On the 25th of September, I urge you all to go to the polling stations," he told the crowd on the final day of campaigning for the Monday referendum.

Hundreds of Iraqis rallied on Friday in Nineveh in protest at the referendum.

The demonstrators waved the national Iraqi flag and carried placards backing the country's territorial integrity.

"This demonstration represents the stance of the Nineveh people, who reject division and partition of Iraq," an organiser of the rally told the gathering.