A diplomatic flare-up has ignited after the Croatian government blocked a private trip by Serbian President Aleksandar Vucic to lay flowers at the site of a World War II concentration camp where tens of thousands of Serbs and others were killed by pro-Nazi authorities in Croatia.
Croatian authorities on July 17 said they only learned of Vucic's planned trip to the site of the former Jasenovac concentration camp through unofficial channels and that such a visit should be "part of arrangements between the two sides."
Croatian Foreign Minister Gordan Grlic-Radman told reporters that "the president of a country is a protected person. Such an arrival requires the involvement of the Croatian authorities."
"We always announce our arrival, but that hasn't happened here. You can't just cross the border."
Serbian authorities immediately reacted by putting restrictions on Croatian officials traveling through its territory.
"From today, all officials of the Croatian state, all holders of official or diplomatic passports, will have to specifically announce and explain their visit or passage through Serbia and will be placed on a special regime of control," Serbian Interior Minister Aleksandar Vulin said.
Serbian Prime Minister Ana Brnabic said Vucic had wanted to visit Jasenovac privately, but that he postponed the trip "for the sake of good relations" between Serbia and Croatia.
"I don't know if he is banned from visiting Croatia or Jasenovac. So he can go anywhere, but not to Jasenovac? Which I think is an incredible precedent," Brnabic said, adding that it was "a brutal trampling on freedom of movement."
Brnabic said Serbia will now request an official visit, "so let's see about these 'European values.'"
Vucic -- a former ultranationalist who solidified his grip on power by reinventing himself as a reformer committed to Serbia's drive toward European Union membership -- has scheduled a July 18 news conference.
On Instagram, Vucic posted a photo of the Jasenovac monument and wrote, "The Serbian people will live and they will never forget!"
During World War II, tens of thousands of Serbs, Jews, Roma, and anti-fascist Croats were killed at the Jasenovac camp -- known as "Croatia's Auschwitz." The camp was run by Croatia's Nazi-allied Ustase regime.
Relations between Serbia and Croatia have been strained since Croatia's declaration of independence from the former Yugoslavia in 1991, which set off a four-year conflict with rebel ethnic Serbs supported by Belgrade.
Many Serbian nationalists have accused Croatia's government of not facing up to the actions carried out on its territory during World War II.
The Croatian government, meanwhile, has accused Belgrade of using the issue for its own internal political reasons and for not dealing with its role in the Balkan wars of 1992-95.