The Serbian Foreign Ministry forwarded a protest note to Croatia on Friday over the burning of the Serbian flag in Knin earlier today during the marking of the 21st anniversary of Operation Storm.
Police arrested two men for setting the flag on fire.
The ministry said in a press release that it "considers this act of vandalism as an undignified and uncivilised gesture which deserves the harshest condemnation and punishment of the perpetrators."
The notes says the Croatian authorities are expected to take every legal step to identify and punish the perpetrators.
This was the fifth note Serbia sent Croatia over the past ten days, accusing Croatia of rehabilitating the Ustasha movement and glorifying convicted terrorists, and over Croatian courts' decisions "against the Serb people."