Mikheil Saakashvili, the former Georgian president, has been appointed the governor of Ukraine's troubled Odessa region, a move likely to antagonise Russia's Vladimir Putin.
The appointment was announced in a post on the website of the Ukrainian president, Petro Poroshenko, on Saturday.
Relations between Ukraine and Russia remain tense following the invasion of parts of eastern Ukraine by Russian troops in August last year.
Odessa, Ukraine's largest seaport, lies between two areas of conflict - the Russia-annexed Crimean peninsula, and the Moldovan separatist region of Transdniester, which is supported by Russian forces.
Saakashvili's appointment is also controversial as the former Georgian leader faces accusation of abuse of power at home and Ukraine has refused to extradite him.
Saakashvili was Georgian president from 2004 to 2013. Under Saakashvili Georgia fought a short war with Russia in 2008, in which it lost control of two Russia-backed separatist territories.
He was outspoken in his support for Ukraine's Euromaidan protest last year and was made an official adviser to President Poroshenko since February 2015.
There was no immediate comment from the Kremlin about Saakashvili's appointment as Odessa governor, but Andre Purgin, a top eastern Ukraine separatist leader, called it a "mockery and an absolutely unprecedented step".
Ian Bremmer, the head of the political risk consultancy Eurasiagroup, warned in a tweet that the situation in Ukraine could deteriorate as a result of the move.
It's an embarrassment for Ukrainian people to be governed by Georgian ex-President. And a provocation to Putin.— ian bremmer (@ianbremmer) May 30, 2015
(Additional reporting from agencies)Reuse content