Ukrainian interim Foreign Minister Andrii Deshchytsia, shown here in May, described Vladi­mir Putin with a vulgar term. (Markus Schreiber/AP)

— Ukrainians have called Vladimir Putin many bad names, among them a Nazi, a dictator and just plain evil. But nothing has caused a firestorm quite like a Ukrainian diplomat’s use of a schoolyard epithet to describe the Russian president during an unscripted moment Saturday night.

Russian lawmakers called Sunday for the dismissal of Ukraine’s interim foreign minister, Andrii Deshchytsia, after he tagged Putin with the swear word. Deshchytsia tossed out the insult breezily as he sought to calm protesters and halt an attack on the Russian Embassy in Kiev.

He had waded into a near-riot as hundreds of people vented their rage at the loss of 49 Ukrainian service members earlier Saturday. Pro-Russian separatists, armed with weapons that many believe were supplied by Russia, shot down a Ukrainian military transport plane as it approached the airport in the eastern city of Luhansk, killing all aboard.

Every window in the three-story Russian Embassy was broken as protesters threw eggs, bricks, paint balls and car parts ripped off diplomatic vehicles.

Deshchytsia pleaded for them to halt the violence. He noted that Ukraine has an obligation to defend embassies and stressed that he was not asking the crowd to stop protesting but to be peaceful.

“I am ready to be here with you and say, ‘Russia, get out of Ukraine,’ ” he said.

Then he spoke the words that would cause an international incident: “Putin is a d---head, yes.”

The remark drew cheers from protesters within earshot and prompted many of them to chant along. A video of the remark was quickly posted to YouTube.

To be sure, Deshchytsia was showing a familiarity with Ukrainian pop culture.

The phrase originated with rival soccer teams, which in March paraded through the eastern city of Kharkiv chanting the phrase in a singsong voice, with the refrain “La la la la la la la la la.” It took off and soon became a staple at soccer games and protests. Ukrainian tourists have taken videos of themselves singing the words, often with embarrassed giggles, while on vacations abroad — at a sake bar in Japan, accompanied by a mariachi band in Los Angeles, sitting in the bleachers at a World Cup game in Brazil.

Even some of the funeral wreaths left on the Russian Embassy’s steps Sunday were adorned with ribbons emblazoned with the phrase.

Geoffrey Pyatt, the U.S. ambassador to Ukraine, rushed to Deshchytsia’s defense on Twitter, praising him “for seeking to defuse a dangerous situation. A skilled diplomat and credit to #Ukraine.”

Deshchytsia, sounding not the least bit chagrined, told the radio station Ekho Moskvy — or Echo of Moscow — that he had been acting in an “emergency situation” in which “the main thing was to restrain the people.”

Nevertheless, Moscow was not amused.

Russian Foreign Minister Sergei Lavrov voiced his displeasure in conversations with the foreign ministers of Germany and France.

Speaking Sunday by telephone to French Foreign Minister Laurent Fabius, Lavrov “expressed indignation at the inaction of the Kiev authorities, who allowed an outrageous act in front of the Russian Embassy in the Ukrainian capital,” the ministry said in a statement.

Leonid Slutsky, a leader in the Russian parliament, said Deshchytsia had violated international agreements on diplomatic conduct.

“When Ukraine’s chief diplomat pours obscenities on the Russian president, in the context of an illegal action that is essentially an aggressive attack on the Russian Embassy . . . this is the apotheosis of what I would call anti-diplomacy,” Slutsky told the RIA Novosti news agency.

Alexei Pushkov, head of the international affairs committee in Russia’s lower house of parliament, said that in retaliation for the slur, Moscow should stop supplying Ukraine with natural gas.

Last-ditch talks on the gas supply appeared to be heading nowhere even before the incident. The talks have deadlocked over pricing, and Russian state-controlled Gazprom has said it will cut off supplies if it does not receive a $1.9 billion payment Monday toward Ukraine’s gas debt.

Because the demand for natural gas is far lower in the summer than in the winter, a cutoff would probably not cause immediate pain in Ukraine or Europe, which gets 15 percent of its gas from Russia via pipelines running through Ukraine. But if a cutoff dragged on, winter supplies could be jeopardized because no gas would be flowing into crucial Ukrainian storage tanks.

Alex Ryabchyn contributed to this report.