Serbia's two journalists' associations have protested the action against Dojcinovic. They said that Russia in 2015 also banned Dojcinovic from entering the country and deported him back to Serbia.
"Such treatment of journalists is unacceptable in the contemporary democratic world," said the Independent Journalists' Association of Serbia.
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"This was a violation of the basic human right to free movement."
The Organized Crime and Corruption Reporting Project (OCCRP) watchdog said in a statement it is deeply concerned by Dojcinovic's detention.
"This is outrageous," said Drew Sullivan, OCCRP's co-founder and publisher. "When a state hosting the world's largest, official anti-corruption gathering denies entry to an invited journalist, it raises serious questions about its commitment."