Syrian air defenses opened fire on Israeli aircraft after they violated Syrian airspace, Syrian officials said Thursday, sharply elevating cross-border tensions.

The aircraft, which had broken the sound barrier as they flew over northern Syria, "dropped munitions" onto deserted areas overnight after coming under Syrian fire, a military spokesman said, according to the official Syrian Arab News Agency.

The incident is likely to stoke concerns that tensions could lead to military conflict between Syria and Israel, though both countries have repeatedly said in recent months that they do not seek a war.

Israel has demanded Syria stop its support for the Hezbollah and Hamas militant groups, which have both been holding captured Israeli soldiers for more than a year.

Syria, in turn, has increasingly pushed its demands for the return of the Israeli-held Golan Heights and is concerned that it is being left out of a U.S.-brokered Mideast peace conference due to be held in November.

Syrian officials did not say how many Israeli aircraft entered its airspace or what type they were. Israel's army spokesman declined to comment, saying he could not discuss military operations.

Syria stopped short of accusing the aircraft of bombing its territory. Asked if Israel had attacked Syria, Syrian Cabinet Minister Buthaina Shaaban said on Al-Jazeera television's English service that the aircraft violated Syrian airspace.

"We are a sovereign country. They cannot do that," Shaaban said.

The Syrian military spokesman said "air defense units confronted" the Israeli aircraft and "forced them to leave after they dropped some munitions in deserted areas without causing any human or material damage."

"We warn the Israeli enemy government against this flagrant aggressive act, and retain the right to respond in an appropriate way," the spokesman said.

The Syrians did not say the aircraft struck targets, and it was not clear what the spokesman meant by dropping munitions. Warplanes sometimes drop extra fuel tanks to make the aircraft lighter and easier to maneuver.

The route the planes flew, east from the Mediterrranean deep inside Syria, brought Israeli warplanes to the closest point to Iran, separated only by Iraqi Kurdistan.

The United States, Israel and some of their allies fear Tehran is using its civilian nuclear program as a cover to produce atomic weapons. Iran denies the charge, saying its program is solely geared toward generating electricity.

Both Israel and the United States have not ruled out airstrikes should the program expand.

It is unclear if, or how often, Israeli aircraft overfly Syria.

Israel acknowledges flying over Lebanon routinely and is believed to fly routine reconnaissance flights over the Golan Heights to monitor Syrian army moves near the disputed territory. Witnesses said Thursday's incident occurred over the other side of Syria, in the al-Abyad area near the northeast border with Turkey near the Mediterranean.

Syrian officials, including President Bashar Assad, have repeatedly warned Israel in recent weeks that the occupation of the Golan Heights "cannot last forever."

Partly as a result of those statements, concerns grew over the summer that tensions along the frontier could escalate into conflict. But both Syrian and Israeli officials publicly and repeatedly said they had no interest in war.

Late last month, Israeli security officials said the army had determined that war with Syria, whose military had reduced its war readiness, was unlikely and Israel began rotating forces out of the Israeli-held Golan Heights.

Israeli counterterrorism expert Boaz Ganor said that if Thursday's overflight occurred, it's possible Israel was "collecting intelligence on long-range missiles" deployed in northern Syria.

Syrian political analyst Imad Fawzi Shoaibi said that Israel may have been probing new air defense systems provided by Russia.

The Syrian military spokesman did not specify whether the military used surface-to-air missiles or anti-aircraft artillery against the aircraft.

Syria is believed to be unhappy that other Arab countries are headed to a peace meeting in November at which the United States hopes for a high-profile meeting between the Palestinians and Israelis, and perhaps also with Saudi officials.

Syria has long disputed any notion that a comprehensive Arab peace deal can be reached unless it also involves some resolution of the Golan Heights, which it wants back in full.

At the beginning of last summer's war against Hezbollah guerrillas in Lebanon, Israeli warplanes buzzed Assad's palace in what analysts called a warning to Damascus. They also flew over Assad's summer home in the coastal city of Latakia, after Syrian-backed Palestinian militants in Gaza captured a young Israeli soldier.

In October 2003, Israeli warplanes bombed a Palestinian guerrilla base near Damascus, the first airstrike since the 1973 war.