Millions of Kurds in Iraqi Kurdistan voted for their independence referendum on Sept. 25 despite severe opposition from Iraq and other countries. Results are expected by Sept. 28. (Joyce Lee/The Washington Post)

Regional powers and Iraq’s central government threatened crippling economic sanctions and military action against Iraq’s Kurdish region on Tuesday, a day after Kurds staged a landmark vote for independence that is emerging as another crisis in a region roiled by civil wars and the fight against the Islamic State.

Iraqi Prime Minister Haider al-Abadi said Kurdish leaders had committed “a strategic and historic mistake” by holding the referendum and gave them until Friday to hand over control of airports and borders in northern Iraq to the federal government. If the order is ignored, international flights to the Kurdish region will be suspended, Abadi said.

Abadi also said that any oil revenue from the Kurdistan region — a critical economic lifeline for the semiautonomous enclave — must be returned to Baghdad, though he did not set a deadline for the demands.

“We will not compromise on Iraq’s unity or sovereignty,” he said. “We have taken measures to impose federal authority according to the Iraqi constitution.”

The orders are the latest signal that Iraq’s central government, along with Turkey and Iran, are holding firm to their pledge to block Kurdish separation from Iraq.

Kurdish leaders have said the nonbinding referendum vote would give them leverage in stalled talks with the Iraqi government over revenue-sharing and borders, despite warnings from the United States that the poll would destabilize the country and potentially the region.

Turkey’s president on Tuesday ramped up his criticism of the referendum, calling it “treachery” against Turkey and threatening to impose a stifling blockade of the Kurdish region in northern Iraq.

The comments by President Recep Tayyip Erdogan were the latest in a series of admonitions by Turkish officials and other regional leaders over the vote, which many Iraqi Kurds see as a critical step toward their long-deferred dream of self-determination.

Iranian state media quoted a military commander Tuesday as saying that new missile batteries have been installed in an area bordering the Kurdish region to “firmly respond to any invasion.” Iran closed its airspace to flights to Iraqi Kurdistan over the weekend.

Ali Akbar Velayati, a top adviser to Iran’s supreme leader, Ayatollah Ali Khamenei, said Iran — which has strong influence over Iraq’s politics and military — will not support a Kurdish secession. He said Kurdish independence would be akin to “creating a second Israel,” state media reported, according to the Associated Press. Israel has been the only country to publicly support the referendum.

Meanwhile, thousands of Iranian Kurds demonstrated Monday night in towns and cities in western Iran, defying their government’s opposition to the vote in a show of Kurdish solidarity.

The Kurdish Democratic Party of Iran, which is based in Iraq, posted video from the demonstrations on social media, showing crowds marching and chanting the Kurdish anthem.

Kurds in Iran have long complained of discrimination, and Iranian authorities worry that fallout from the referendum could stir further unrest.

The results of the referendum have not been fully tallied, but officials expect an overwhelming yes on independence — the first step on a possible path toward a break with Baghdad.

Kurdish Regional Government President Masoud Barzani responded to the increasingly dire rhetoric out of Baghdad, Ankara and Tehran in a televised speech late Tuesday, saying that the referendum was not meant to immediately “draw new borders” but instead to begin discussions on how to become “good neighbors.”

“The only way to solve our problems is through discussion and understanding, not through threats,” said Barzani, adding that the international community should support the democratic exercise by the Kurds. 

The vote was opposed by virtually all of the Kurds’ allies and neighbors, including the United States and Iran. Turkey, which has fought for decades against Kurdish separatists at home, has reacted with growing anxiety as Kurdish groups have gained strength and influence across its borders in Syria and Iraq.

Erdogan’s barbed comments Tuesday appeared to be part of a broader international effort to shape the vote’s aftermath and push the Kurdistan Regional Government and the Iraqi government toward an accommodation the region could accept.

Erdogan, speaking in the Turkish capital, Ankara, warned that Turkey could cut off oil exports from northern Iraq and stop trucks from moving across the border.

Iraq’s Kurdish region also borders Syria and Iran, but Turkey is the main commercial lifeline to international markets.

But as Turkey continued to denounce the referendum, Western nations began to soften their tone.

In a statement, the State Department said that the United States “is deeply disappointed” the regional government held the vote but that the “historic relationship with the people of the Iraqi Kurdistan Region will not change.” 

It did reiterate, however, the U.S. belief that the referendum “will increase instability and hardships for the Kurdistan region and its people” by compromising relations with Baghdad and neighboring countries. Washington also fears that the plebiscite could give extremists an opening to exploit.

 Britain’s ambassador to Iraq, Frank Baker, said in a Twitter post Tuesday that his country’s long ties with the Kurdish government will continue, including in the battle against the Islamic State.

Kurdish media began publishing unofficial returns from polling stations Tuesday showing that with about 10 percent of votes counted, yes votes were coming in at an overwhelming 93 percent.

Kurdish election authorities said official results would be released by Thursday.

Fahim reported from Istanbul. Erin Cunningham in Istanbul contributed to this report.