Kosovo’s opposition on Wednesday held up ratification of a border agreement with Montenegro, which they regard as a sell-out, releasing tear gas at a parliamentary session called to push the deal through, according to Reuters.

Approving the 2015 border deal is a key condition for Kosovo to gain visa-free travel to the European Union, but the opposition party Vetevendosje is adamantly against it, claiming it will wrongly surrender some 8,000 hectares (30 square miles) of Kosovan territory to its neighbor.

lawmakers threwcanisters into the chamber to block discussion and a vote, causing deputies to withdraw choking and spluttering.

The session was adjourned to allow the chamber to ventilate but as MPs started going back into the room, more tear gas was released.

It was not clear when proceedings would restart.

The EU commissioner for enlargement, Johannes Hahn, condemned the action in a tweet, saying: “Such behavior has no place in a democracy.”

“On this important day, Kosovo leaders must assume their responsibilities and vote for the demarcation agreement,” he said.

U.S. ambassador to Kosovo, Greg Delawie, commented to reporters: “This should not be happening in a European country. Teargas is not a European thing.”

The EU and the United States remain the biggest supporters of Kosovo, politically and financially.

Kosovo is the only country in the Balkans whose citizens need visas to travel to EU member states. Its regional neighbors Serbia, Albania, Montenegro, Macedonia and Bosnia obtained visa-free access to Europe’s border-free Schengen zone in 2010.

Kosovo declared independence in 2008, nearly a decade after NATO air strikes drove out Serbian security forces accused of killing and expelling ethnic Albanian civilians during a counter-insurgency war.

To move toward membership in the European Union which the government has set as its goal, Kosovo needs to soothe relations with its neighbors including Serbia which refuses to recognize Pristina institutions.