Belarus has ordered the closure of the office of the Organization for Security and Cooperation in Europe (OSCE) in the capital Minsk.
"The Belarussian side has taken the decision not to prolong the mandate of the OSCE office in Minsk," AFP quoted Foreign Ministry spokesman Andrei Savinykh as saying on Friday.
Savinykh said the decision was made because the office's mandate "had been fulfilled."
"It needs to be said that this is a conscious decision caused by the lack of objective reasons for retaining an OSCE mission in Belarus," he added.
Incoming OSCE chair Lithuania and Germany have condemned the move.
In a statement issued on Friday evening, Lithuanian Foreign Minister Audronius Azubalis also urged Minsk to review the decision.
"Its [OSCE] mandate has not been completed. There is an important job for the OSCE to continue in Belarus," Azubalis said, as Lithuania geared up to take over the OSCE chairmanship from Kazakhstan through 2011.
The OSCE opened a branch office in Minsk in 1998.
The OSCE branch in Belarus was closed not long after its monitors issued a report about voting irregularities during the recent presidential election.
The Belarus Central Election Commission has declared incumbent President Alexander Lukashenko the winner of the poll.