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The mission, which arrived after Kosovo declared independence in 2008, still has 105 special police officers from Poland who are given the responsibility of intervening in tough situations.
The new unit of 92 members from the European Gendarmerie Force are from Portugal, France and Italy, and will be posted temporarily.
Mission spokeswoman Ioanna Lachana said the new unit was a response to a need for more troops and to better support Kosovar troops if requested.
“However, Russia's invasion in Ukraine puts everything in a different light,” Ms Lachana told Reuters.
Nato has 3,770 troops to maintain the fragile peace in Kosovo, mainly in the northern part of the country where about 50,000 local Serbs, backed by Belgrade, refuse to recognise Kosovo's authority and are calling for partition among ethnic lines to unite with Serbia.
Serbia and its traditional ally Russia do not recognise Kosovo’s independence.