Tear gas was lobbed into the Kosovo parliament on Wednesday halting a vote on a border deal with Montenegro seen as key for Pristina's bid to join the EU.
The agreement, negotiated with Montenegro in 2015, is crucial for Kosovo to obtain visa-free travel in the European Union and eventually join the bloc.
With thick smoke filling parliament all MPs had to evacuate, an AFP correspondent said.
It was unclear who exactly threw the tear gas canister but it came from the area of benches occupied by MPs from the main opposition nationalist leftist Vetevendosje (Self-Determination) party.
The party is firmly opposed to the border deal claiming it would deprive the Balkan nation of several thousand hectares of land.
Vetevendosje MPs have repeatedly released tear gas as a protest in parliament in the past.
The session was first briefly interrupted but when it resumed at around 1.15pm (1215 GMT), more tear gas was thrown forcing the lawmakers to leave the hall again.