UNITED NATIONS — As tensions between Syria and Israel increased yesterday with allegations in Damascus of an infringement of its airspace, Jerusalem officials accused Moscow of instigating the heightened border alert that has threatened to ignite war between the countries all through the summer.

The assertion by Syria that it shot at Israeli aircrafts yesterday that flew in a “flagrant aggressive act” over its northern territory was accompanied by warnings from high officials in President Assad’s government, saying they would “respond in an appropriate way.” Israeli officials from Prime Minister Olmert down declined to confirm or deny that an incident took place.

“This is a very worrisome situation,” a Russian diplomat at the United Nations, speaking on condition of anonymity, told The New York Sun yesterday, referring to Syria’s allegations. He echoed a Foreign Ministry statement in Moscow that cited the Damascus report to warn Israel against employing military force.

According to Damascus its air defense units shot at Israeli crafts that entered Syrian air space before sunrise yesterday morning. The official statement did not say whether the crafts were planes, drones, or other flying objects. It placed the incident near the Turkish border, where according to recent press reports Russia is building a naval base in an attempt to increase its military presence in the Mediterranean.

Yesterday’s Syrian allegation comes at the end of a summer in which the national armies on both sides of the Israeli-Syrian border beefed up their presence, even as politicians in Damascus and Jerusalem — publicly and through proxies — exchanged calming messages and denied war preparations. Israeli officials recently began to accuse Russia of instigating the border tension.

“At a certain time the Russians caused the Syrians to believe that Israel was preparing for war,” a top Ministry of Defense official, Amos Gilad, told Israel Army Radio yesterday. “I think that they have stopped this,” he added, meaning the Russians. “Syria is not planning an attack on Israel, and Israel is definitely not planning on attacking Syria.”

But even as both sides do not want it, events such as yesterday’s alleged airspace violation “could lead to a classic case of miscalculation that would result in an all-out war,” a former deputy security adviser to Prime Minister Sharon, Chuck Freilich, told the Sun.

After last year’s Lebanon war, Israel is not eager to start a new war, Mr. Freilich said. But it also wants to avoid being caught unprepared again, which could explain the military drills near the Syrian border. Extremists among members of the Assad regime may well have been encouraged by Hezbollah’s boasts last year of victory over Israel, and may want to imitate such success.

“Moscow is playing a very dangerous game” by adding to this volatile mix, Mr. Freilich said.

Russia is a “strategic threat to Israel,” Yaacov Amidror of the Jerusalem Center for Public Affairs told the Sun. A former top strategist in the Army Intelligence unit, Mr. Amidror said Israel should rethink its close bilateral relations with Russia, as Moscow’s interests clash with those of Israel.

“The Soviet Union saw Israel as its enemy, which is not the case today,” Mr. Amidror said. Nevertheless, as it tries to further its sphere of influence in the region, Moscow’s actions “could be very harmful for us,” he said. “Military aid and diplomatic support for Iran and Syria present a real threat to Israel.” Another “classic example” of the threat Russia presents, he said, is its naval buildup in the eastern Mediterranean, where the Soviet Union once had a very strong presence.

Last year, the Moscow business daily Kommersant quoted an anonymous defense ministry source as saying that the northern Syrian port city of Tartus was designated as a new base for Black Sea Fleet warships, which would be redeployed from the Ukrainian port of Sevastopol. Other reports cited intelligence satellite data confirming the buildup at Tartus. The Russian defense military officially denied the Kommersant report. But a former intelligence officer in Jerusalem, who spoke on condition of anonymity, said yesterday that Israel has been following the Tartus buildup closely, and it could possibly explain the presence of a reconnaissance craft where Syria alleged that yesterday’s incident took place, adding, however, that he had no first hand information on the incident.

Israel’s army spokesman declined comment on military operations. Prime Minister Olmert, speaking during a nationally televised address to leaders of his Kadima Party, did not even mention the Syrian allegation. “I don’t know what you are talking about,” he told reporters who asked him about it afterward, according to the Ha’aretz newspaper.

Syria’s U.N. ambassador, Bashar al-Jaafari, told reporters yesterday that his country planned to raise the issue with the Security Council soon, adding he was awaiting instructions from Damascus. As of last night no one requested to convene the council, said a diplomat from the French mission to the U.N., which serves as the council’s rotating president in September. A Russian diplomat said Moscow does not expect any council action before its U.N. ambassador, Vitaly Churkin, returns to New York next week.