By ALEXANDER PERSONSZELIS/AFP/Getty ImagesBulgaria has said it will allow its people to return home on Tuesday to avoid a humanitarian crisis.
Serbia and Croatia declared war on each other in August, and tensions between them have remained high since.
Serbian Prime Minister Zoran Milanovic said the situation is “dangerous”, and he warned that the border would be closed in a matter of hours.
“We must ensure that it is not possible for Croatia and Serbia to enter each other’s territory,” Milanovic told the state-run RTS television station.
Croatia’s Defence Minister Zdenek Zeman said his country will not allow its citizens to cross the border into Serbia and said he would try to stop the border crossing.
Seria’s Foreign Minister Milan Chovanec said Croatia should be ready to open the border if needed.
Croats are worried about the humanitarian situation and want to go home soon, but their government has said the border will be closed as soon as possible.
Bulgarians have been asking to be allowed to go back to their homes since August, but Serbia says they must stay at their own country’s border.
Bulgarian Foreign Minister Nikola Zinchenko has said Serbia’s actions have violated international law.
Serbians and Bosnians have a history of conflicts.
The last time the two countries fought was in 1991, when Serbian forces invaded.
The war ended with an agreement to keep the two sides apart.
The war in Bosnia ended in 1999.