The ex-servicemen accused Serbs of turning an Orthodox Christmas party in a wartime flashpoint village into a display of nationalism.
The Croatian war veterans’ association from the town of Vukovar demanded a response from the authorities after a three-minute video of the celebration in the village of Borovo Selo was posted on YouTube.
One angry comment posted on the Croatian government’s Facebook page asked the country’s leadership “how it could allow something like that”.
The YouTube video shows a long column of cars decked with Serbian flags honking their horns as it cruises through the village.
Youths in traditional Serbian hats also make three-finger salutes – images which the veterans identified with the ‘Chetnik’ paramilitary units that operated during the war in Croatia from 1991 to 1995.
Twelve Croatian policemen were killed in Serb-populated Borovo Selo in May 1991, in a clash between Serbs and Croats which is seen by many as the beginning of the war in Croatia.
Borovo Selo was a Serbian military stronghold during the three-month siege of Vukovar, which was seized and destroyed by Serb forces and the Yugoslav Army in November 18, 1991.
Around 1,500 people was killed during and after the siege.
A police spokesman in Vukovar confirmed that there had been an Orthodox Christmas party in Borovo Selo, but said that officers had ensured security and a Croatian flag had been on prominent display.