Iraq’s ethnic Kurds voted an emphatic “yes” in a pivotal independence referendum for their autonomous region in the north, officials said, sending shockwaves across the region.

The Kurds, who have ruled over the area in Northern Iraq since the 2003 US invasion, held the referendum in defiance of Baghdad, which considered it illegal.

The Iraqi Kurdish leadership billed Monday’s vote as an exercise in self-determination, but the Iraqi government strongly opposed any redrawing of its borders.

Kurdish officials said the referendum passed easily, but the official count isn’t expected before Wednesday.

The United States and major European countries strongly opposed the vote, which they described as destabilizing at a time when all sides are still fighting against ISIS militants.

Turkey and Iran were also concerned, fearing the move will embolden their own Kurdish populations to seek an independent state.

On Tuesday, Iraqi Prime Minister Haider al-Abadi said the vote was a “historic and strategic mistake by the Kurdish leadership” and demanded they turn over control over their airports or face a flight ban.

“I will not give up on the unity of Iraq. That is my national and constitutional duty,” he said, adding that any ban would still allow for humanitarian and other “urgent” flights.

Masoud Barzani, the Kurdish regional president who spearheaded the referendum, called for “dialogue” with Baghdad.

“Negotiations are the right path to solve the problems — not threats or the language of force,” he said.

After the polls closed on Monday night, the skies above Irbil were illuminated by fireworks and families flocked to the center of town to celebrate.

Across the border, thousands of Iranian Kurds held rallies in support.

Iraq’s al-Abadi ordered the country’s Kurds to turn control of their region’s airports over to the government by Friday or face a flight ban.

Iran’s paramilitary Revolutionary Guard and its regular army have been running military exercises near the border with Iraq’s Kurdish region in a sign of Tehran’s displeasure at the Kurdish referendum.

And Turkish President Recep Tayyip Erdogan reiterated on Tuesday that his country is considering all options, ranging from military intervention to economic sanctions, against Iraq’s Kurdish region.

With Wire Services