Turkey threatened military action and Iran closed its border with Iraqi Kurdistan yesterday as a controversial independence referendum went ahead in the region.

Iranian Foreign Ministry spokesman Bahram Ghasemi said: “At the request of the Iraqi government, we have closed our land and air borders” with the semi-autonomous region.

He reiterated Tehran’s stance — shared by Iraq, Syria and Turkey — that the unofficial vote was “illegal and illegitimate.”

On Sunday, Kurdistan regional government (KRG) President Masoud Barzani admitted that hold the referendum was “risky,” but insisted: “We are ready to pay any price for our independence.”

Mr Barzani’s opponents in Iraqi Kurdistan accuse him of using the poll to strengthen his own grip over the KRG.

Yesterday, Turkish Prime Minister Binali Yildirim suggested that his country’s south-eastern border with Iraq could be closed as well.

Turkey’s President Recep Tayyip Erdogan went further, claiming that opposing the Iraqi Kurdish vote was a “matter of survival” for his country.

He also threatened to escalate week-long military manoeuvres on the border into an invasion. ”Our military is not there for nothing,” Mr Erdogan said. “We could arrive suddenly one night.”

The Turkish military said that air force jets had bombed ammunition dumps and gun emplacements of the Kurdistan Workers Party (PKK) — arch enemies of both the KRG and Turkey — in northern Iraq.

At the United Nations in New York, Syrian Foreign Minister Walid al-Moallem said on Sunday: “We reject any measure the leads to dividing Iraq.”

And the Iraqi Communist Party questioned the timing of the referendum amid the war against Isis.

While insisting changes to the country’s federal constitution “cannot be decided unilaterally by a particular party,” it warned it would be a “grave mistake” to “to resort to violence and military action” to solve the crisis.