The European Union on Monday condemned what it called the "divisive and inflammatory" celebration of the Bosnian Serb territory's 30th anniversary.
The "Republika Srpska" (RS) marked its so-called national day on Sunday with a parade of police and military veterans and renewed calls for secession.
But Brussels, in a statement from the spokesperson for its foreign service, warned that these actions are "further escalating the ongoing political crisis."
The statement said that the Serb celebrations were "not in line" with Bosnia's constitution nor the country's stated goal of eventual EU membership.
"RS leadership should contribute to ending a worrying trend of hatred and intolerance," the statement said.
"This must include putting an end to the glorification of war criminals and to denying or glorifying their crimes."
Last month, RS leader Milorad Dodic, the Serb member of Bosnia's tripartite presidency, set in motion plans to withdraw from Bosnia's central institutions.
The move earned fresh financial sanctions from the United States, with Washington chiding Dodic for attempting to undermine the landmark peace deal that brought an end to Bosnia's 1992-95 war.
But at Sunday's March, he declared: "There is no freedom for the Serb people if they don't have their state."
The 1995 peace deal effectively split Bosnia in two, with one half given to the ethnic Bosnian Serbs and the other to be ruled by a Muslim-Croat federation.
Sunday's celebrations marked 30 years since the Serbs' unilateral declaration of the RS, three months before the start of the siege of Sarajevo and the conflict that would claim some 100,000 lives.
