Serbia denounced Israel on Monday for taking part in a ceremony in Croatia marking a victorious 1995 offensive against rebel Serb-held territories.
"It's sad that an Israeli flag flew yesterday at the celebration of that criminal action," Serbian Foreign Minister Ivica Dacic told a private Belgrade television station.
"We are very disappointed," he said.
He said it was "immoral" that Israel took part in the commemoration when tens of thousands of Jews, as well as Serbs and Gypsies, perished in Croatian concentration camps during World War II.
Serbia considers Israel its close ally, with a common history of suffering of their peoples during the war.
Three Israeli Air Force F-16s took part in a flyby in Sunday's ceremony, which marked the anniversary of the operation that restored Croatia's control over land held by rebel Serbs during the 1991-1995 war. Serbian officials have compared the offensive, known as Operation Storm, to the actions of Nazi Germany.
A statement from the Israeli Embassy in Belgrade said that the participation of Israeli jets was related "solely" to Croatia's announced purchase of 12 Israeli F-16s.
"This has no political elements or any connection to the historic relations between Serbia and Croatia," the statement said. "The solid friendship that exists between Israel and Serbia will never be jeopardized in any way."
Even before the flyby, top Nazi hunter Efraim Zuroff criticized the appearance of Israeli jets at the ceremony in Croatia.
"Very upset that Israeli Air Force jets will be flying in event to mark 'Operation Storm,' during which Croatia expelled 250,000 Serbs from their homes in Croatia," Zuroff tweeted. "Until today no foreign country has ever participated."
Top Croatian officials attended the ceremony, held in the former rebel stronghold of Knin, and hailed the offensive as a flawless military action that ended Croatia's war for independence and reunited its lands.
U.S. military envoys were also among the guests at the event.
Operation Storm "has become a textbook successful military operation," Croatian President Kolinda Grabar-Kitarovic said.
"It was the time of total unity of the Croatian people and Croatian soldiers."
Meanwhile, Serbian President Aleksandar Vucic, who was an extreme Serb nationalist during the war, accused Croatia late Saturday of intentionally expelling Serbs from the country because of their ethnicity.
Speaking of Operation Storm to a crowd of thousands at a commemoration event in northern Serbia, Vucic mentioned Anne Frank, the Jewish teenager killed in the Holocaust whose diary became famous worldwide, saying she was persecuted for the same reason as the Serbs in Croatia.
"The intent was the same. Hitler wanted a world without Jews; Croatia and its policy wanted a Croatia without Serbs," Vucic said.
Croatian officials rejected Vucic's analogy.
"This is really too much," Prime Minister Andrej Plenkovic was quoted as saying by Croatian public broadcaster HRT.
And Croatian Defense Minister Damir Krsticevic said, "We didn't start the war. We defended ourselves and later liberated Croatia."
The liberal Index news portal described the Serbian president's statement as "scandalous" and asked if Vucic should be barred from entering 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.
