President Recep Tayyip Erdoğan has threatened to invade Iraq, after the country's Kurds voted for independence in a non-binding referendum.
Issuing a strongly-worded speech, Mr Erdoğan said fighting the Iraqi Kurdish bid for independence was "a matter of survival".
The Turkish leader also suggested he could cut off a pipeline that carries oil out of Iraq, to increase pressure on an autonomous Kurdish region.
Mr Erdoğan has long struggled against a Kurdish insurgency in southeast Turkey, which shares a border with northern Iraq.
Baghdad also did not recognise the referendum, which it sees as a Kurdish attempt to exert more control over the country's oil reserves.
Mr Erdoğan's indication that he could cut the pipeline came shortly after Prime Minister Binali Yildirim said Ankara could take punitive measures involving borders and air space against the Kurdistan Regional Government (KRG) over the referendum.
Voting began on Monday despite the strong opposition from governments in the region. Western governments, too, had objected to the poll, fearing the move could aggravate Middle East instability.
Mr Erdoğan said the “separatist” referendum was unacceptable and that economic, trade and security counter-measures would be taken.
Pointing to Turkish military exercises currently taking place on Turkey’s border with the Iraqi Kurdish region, Mr Erdoğan said: “Our military is not (at the border) for nothing." He added: “We could arrive suddenly one night.”
Suggesting that Turkey could halt oil flows from a pipeline from northern Iraq, he said: “After this, let's see through which channels the northern Iraqi regional government will send its oil, or where it will sell it. We have the tap. The moment we close the tap, then it's done.”
Yet he stopped short of saying Turkey had decided to turn off the oil flow. Hundreds of thousands of barrels of oil a day come through the pipeline in Turkey from northern Iraq.
Mr Yildirim said Ankara would decide on punitive measures against the KRG after talks with Iraq's central government.
“Our energy, interior and customs ministries are working on (measures). We are evaluating steps regarding border gates and air space. We will take these steps quickly,” Mr Yildirim told Turkish broadcasters.
Iraqi soldiers arrived in Turkey on Monday night to join a drill on the Turkish side of the border near the Habur area in the southeast, Turkey's military said in a statement. Iraq's defence ministry said the two armies started “major manoeuvres” at the border area.
Local media said Turkey had blocked access to the KRG via the Habur border crossing with Iraq. Ankara's customs minister denied this, saying Habur remained open but with tight controls on traffic, according to the state-run Anadolu agency.
However, Mr Erdoğan later said traffic was only being allowed to cross from the Turkish side of the border into Iraq.
Maruf Ari, a 50-year-old truck driver, was one of those who had crossed back into Turkey early on Monday morning. He said a closure of the gate would ruin his livelihood.
“If the border is closed it will harm all of us. I (have been) doing this job for 20 years. I'm not making a lot of money. Around 1,000 lira (£209) a month. But if the gate is closed, we will go hungry.”
The United States and other Western powers also urged authorities in the KRG to cancel the vote, saying it would distract from the fight against Islamic State.
“We will continue to take determined steps and the Kurdistan Regional Government must take a step back. It is an absolute must,” Mr Erdoğan said.
Shares of Turkish Airlines, which has direct flights to northern Iraq, tumbled 6.5 per cent in the BIST 100 index. Turkey's currency, the lira, also weakened.
Turkey took the Kurdish television channel Rudaw off its satellite service TurkSat, a Turkish broadcasting official told Reuters.
Turkey has long been northern Iraq's main link to the outside world, but sees the referendum as a grave matter for its own national security. Turkey has the region's largest Kurdish population and has been fighting a three-decade insurgency in its mainly Kurdish southeast.
On Saturday, Turkey's parliament voted to extend by a year a mandate authorising the deployment of troops in Iraq and Syria.
But Turkey is unlikely to make rash moves when it comes to sanctions against the KRG, said Nihat Ali Ozcan, a professor of political science and international relations at TOBB University of Economics and Technology.
“Closing the border gate, cancelling international flights and, at the final step, cutting the pipeline can be discussed,” he said. “Military pressure can be used directly or indirectly.”
The Turkish army launched military exercises involving tanks and armoured vehicles near the Habur border crossing a week ago and they are expected to continue until at least 26 September. Additional units joined the exercises as they entered their second stage.
Turkey's military said in its statement that the third phase of the drill would be held on 26 September and that Iraqi soldiers who arrived on Monday night would join.
The military has also in recent days carried out daily air strikes against Kurdistan Workers Party (PKK) targets in northern Iraq, where the group's commanders are based.
There are around 30 million Kurdish people scattered across several countries following the collapse of the Ottoman Empire a century ago.
The PKK launched its separatist insurgency in 1984, and more than 40,000 people have been killed since. It is designated a terrorist group by Turkey, the United States and European Union.
In a travel warning, Turkey strongly recommended its citizens in the Iraqi Kurdish provinces of Dohuk, Erbil and Sulaimaniya leave as soon as possible if they are not obliged to stay.
Agencies contributed to this report
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