Croatia on Sunday celebrated a victorious 1995 military offensive in which it retook lands held by rebel Serbs, while Serbia's president compared the operation to the policies of Nazi Germany.
The comments by Serbian President Aleksandar Vucic have whipped up tensions between two main Balkan rivals whose conflicting views illustrate persistent divisions stemming from the 1991-95 war.
The war in Croatia erupted when the country declared independence from the former Yugoslavia. Minority Serbs in Croatia, backed by Serbia, took up arms and formed their own self-declared state, rejecting the split from the Serb-led Yugoslav federation and expelling hundreds of thousands of Croats from their homes.
More than 10,000 people were killed and many Croatian towns were devastated in the years that followed before Croatia in August 1995 took back control of the Serb-held lands. That blitz attack, dubbed Storm, sent 200,000 minority Serbs fleeing the country in miles-long columns of tractors, cars and horse-driven carts.
Croatia on Sunday hailed the offensive as a flawless military victory that reunited the country's territory and ended the war. Top officials attended a central ceremony in the former rebel stronghold of Knin that included a fly over by military jets.
U.S. and Israeli military envoys were among the guests attending the event, while Israeli jets took part in the fly by, Croatia's defense ministry said.
"[Storm] has become a textbook successful military operation," said Croatian President Kolinda Grabar-Kitarovic. "It was the time of total unity of the Croatian people and Croatian soldiers."
Meanwhile, neighboring Serbia mourned the hundreds of victims who were killed during the 1995 attack.
Vucic, an extreme Serb nationalist during the war, accused Croatia late Saturday of intentionally expelling Serbs from the country because of their ethnicity. Vucic evoked the fate of Anne Frank, the world famous Jewish diarist who died in the Holocaust, saying she was persecuted for the same reason as the Croatian Serbs.
"The intent was the same. Hitler wanted a world without Jews; Croatia and its policy wanted a Croatia without Serbs," Vucic told thousands at a commemoration event in northern Serbia.
Vucic's strongly-worded comments have been rejected by Croatia. The liberal Index news portal described the Serbian president's statement as "scandalous" and asked if Vucic should be barred from entering Croatia.
Croatian Defense Minister Damir Krsticevic retorted that "we didn't start the war, we defended ourselves and later liberated Croatia."
Vucic has said he wants to boost cooperation with other Balkan nations and lead Serbia toward membership in the European Union, but he also has been increasing military and other ties with Russia.