Italy summoned Croatia's ambassador to the foreign ministry and canceled a government official's visit to Zagreb after angry exchanges over a speech by Italy's president commemorating World War II massacres by Yugoslav partisans.
The dispute has revived grudges dating back six decades.
It began with Italian President Giorgio Napolitano's speech on Saturday to mark the deaths of thousands of Italians who were pulled from their homes, tortured and shot by Communist Yugoslav partisans during and at the end of the war.
Some victims were thrown -- sometimes still alive -- into alpine crevasses known in local dialect as foibe, and the atrocities became known as the foibe killings.
"There was a wave of hate and bloody fury, and a Slavic expansionist design ... that took on the sinister appearance of an ethnic cleansing," Napolitano said.
The response from Croatia, which was part of Yugoslavia until 1991, was chilly.
President Stipe Mesic said on Monday that Napolitano's speech contained "traces of open racism, historical revisionism and political revanchism."
Mesic said on Tuesday that he would suggest that Italy and Croatia form a commission of forensics experts to investigate how many people died in the killings.
The comments prompted Italian Minister of Foreign Affairs Massimo D'Alema to accuse Mesic of distorting the words of the president and to summon the Croatian ambassador.
In their meeting, D'Alema told the ambassador he was "stunned and pained" by Mesic's words and insisted that there was no reason for the criticism of the Italian president's speech, ministry officials said.
They said that the envoy assured D'Alema he would relay Italy's sentiment to his country's authorities.
D'Alema canceled a visit to Croatia by Foreign Affairs Undersecretary Bobo Craxi, which had been scheduled for yesterday.
Thousands of Italians were tortured and killed in Trieste, Gorizia and on the Istrian peninsula between 1943 and 1945 by Yugoslav Communists on anti-fascist rampages.
The number is unclear, but some estimates put the figure at around 10,000.
Trieste, now part of Italy, and the Istrian peninsula -- most of which is now in Croatia -- came under Italian control after World War I and they were brutally "Italianized'' under dictator Benito Mussolini's fascists.
Official Yugoslav postwar figures showed that about 80,000 Croats, Serbs and Montenegrins perished during the Italian occupation of Dalmatia and Montenegro in 1941 to 1943.
Memories from that time prompted the revenge killings as World War II wound down and Yugoslavs entered the region.
Many ordinary citizens were killed and tortured simply for being Italian or being hostile to annexation by Yugoslavia.
While not denying the killings, some Croatians condemn efforts that remember the victims without addressing the whole history of the tragedy.