The world's largest security body said on Thursday it was officially winding up its observer mission in Ukraine after eight years, after Russia vetoed its extension.
The Organization for Security and Cooperation in Europe (OSCE) said in a statement it would "take immediate steps" to close the mission after members failed to find a way around Russia's objections during a meeting last month.
Poland's Foreign Minister Zbigniew Rau, whose country holds the rotating OSCE chairmanship, said the organisation had tried all options but "the position of the Russian Federation left us with no choice".
The Vienna-based OSCE's mission to Ukraine began in 2014 after Russia-backed separatists launched an insurgency in the east.
The organisation was the only international body monitoring the conflict on the ground.
OSCE monitors were largely withdrawn from the country following Russia's full-scale invasion in February.
But the administrative staff were left behind, and four of them have since been detained.
OSCE Secretary General Helga Maria Schmid said the organisation would continue to push for an "end to the detentions, intimidation, and disinformation that are so dangerous for our national mission members".
The OSCE has 57 members on three continents — including Russia, Ukraine and the United States.
