President Tayyip Erdogan warned on Monday Turkey could cut off the pipeline that carries oil from northern Iraq to the outside world, intensifying pressure on the Kurdish autonomous region over its independence referendum. He also threated military intervention in Iraq, saying that Kurdish independence was unacceptable to his country, and that this was a 'matter of survival."

Erdogan spoke shortly after Prime Minister Binali Yildirum said Ankara could take punitive measures involving borders and air space against the Kurdistan Regional Government (KRG) over the referendum and would not recognize the outcome.

>> Follow live updates from the Kurdish referendum >>

President Tayyip Erdogan warned on Monday Turkey could cut off the pipeline that carries oil from northern Iraq to the outside world, intensifying pressure on the Kurdish autonomous region over its independence referendum. He also threated military intervention in Iraq, saying that Kurdish independence was unacceptable to his country, and that this was a 'matter of survival."

Erdogan spoke shortly after Prime Minister Binali Yildirum said Ankara could take punitive measures involving borders and air space against the Kurdistan Regional Government (KRG) over the referendum and would not recognize the outcome.

Open gallery view A member of Peshmerga forces shows his ink-stained finger during Kurds independence referendum in Sheikh Amir village, Iraq, September 25, 2017. Credit: THAIER AL-SUDANI/REUTERS

>> Read more on the Kurdish referendum: Netanyahu, sole leader to endorse independent Kurdistan, hits back at Erdogan for supporting Hamas ■ One day in September could wreak havoc in the Middle East ■ As Israel backs Kurdish independence, Palestinians may reap the benefit >>

He stopped short of saying Turkey had decided to close off the oil flow. Hundreds of thousands of barrels of oil a day come through the pipeline in Turkey from northern Iraq, but he made clear the option was on the table.

“After this, let’s see through which channels the northern Iraqi regional government will send its oil, or where it will sell it,” he said in a speech. “We have the tap. The moment we close the tap, then it’s done.”

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,” Yildirim told Turkish broadcasters.

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.

“It seems all quiet. We don’t have any difficulties passing the border from both sides,” said Maruf Ari, a 50-year-old truck driver who crossed back into Turkey from Iraq on Monday morning.

“If the border is closed it will harm all of us. I‘m doing this job for 20 years. I‘m not making a lot of money. Around 1,000 lira ($285) 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.

Parliament Vote

Shares of flag carrier Turkish Airlines, which has direct flights to northern Iraq, fell nearly 4 percent, underperforming a 1.75 percent decline in the BIST 100 index. Turkey’s lira currency also weakened.

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 authorizing the deployment of troops in Iraq and Syria.

The KRG exports hundreds of thousands of barrels of oil per day through Turkey to international markets, in defiance of Iraq’s central government.

With that in mind, 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 armored vehicles near the Habur border crossing a week ago and they are expected to continue until Sept. 26. Additional units joined the exercises as they entered their second stage.

The military has also in recent days carried out daily air strikes against Kurdistan Workers Party (PKK) militant targets in northern Iraq, where the group’s commanders are based.

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.