The Israeli army said three Syrian tanks entered the demilitarized zone in the Golan Heights on the Israel-Syrian border Saturday.
The Israel Defense Forces raised its alert level in the Northern Command area, and a military spokeswoman said Israel complained to the U.N. peacekeeping force in the area after the tanks entered.
The incident — the first such violation in 40 years — was not regarded as an incident of hostility toward Israel. Rather, the Syrian tanks were apparently facing off against Syrian rebel forces. Nonetheless, Syrian-Israeli relations are relentlessly fraught, and any border incident raises tensions.
Hebrew news site Ynet said there were reports that two Syrian armored personnel carriers also crossed into the zone.
The Syrian army vehicles were deployed just a few miles away from Israeli military positions.
Several mortar shells from the Syrian fighting have reportedly fallen in the same area in recent days, and one of them may caused a small fire.
The DMZ (Demilitarized Zone), which is about 7 kilometers (3.5 miles) at its widest and 200 meters (yards) at its narrowest, was created after the 1973 war in which Syria tried to retake the strategic plateau.
Marco Carminjani, an official with the U.N. body supervising the zone, said he could not immediately confirm the entry of the tanks. But if the report is true, he said, it would be a violation of the 1974 disengagement agreement between Syria and Israel. He said it would be the first such move in the zone since the accord.
There have long been concerns in Israel that violence from Syria’s civil war could spill across the long-quiet frontier. Misfired Syrian shells have exploded inside Israel on several occasions in recent months, and the Mount Hermon tourism site was briefly closed after suspicious movements in the area.
In late September, a rocket fired from Syria landed in the central Golan Heights. A day earlier, several mortar shells from Syria had fallen in agricultural land in the northern Heights in the first reported instance of munitions spillover from the Syrian civil war into Israel.
In July, Jerusalem complained to the UN over the incursion of Syrian soldiers into the DMZ during fighting with rebel forces.
Israel has worried that the conflict could affect the Golan, and in July took steps to avoid an influx of refugees from Syria. Fighting has broken out near the border with Israel before; in July, Defense Minister Ehud Barak watched from the border as rebels battled regime forces nearby, and the proximity of the fighting sparked a mini-tourism trend.
Earlier this summer, the IDF held surprise exercises in the area to simulate a response to a sudden attack.
Israel captured the Golan Heights from Syria in the 1967 Mideast war and extended Israeli law to the area.
Israel’s Foreign Minister Avigdor Liberman, touring the Golan Heights last Tuesday, said the territory would stay in Israeli hands, calling it non-negotiable under a Likud-Yisrael Beytenu government.
“The Israeli Law, which applies to the Golan Heights, has been in place since the days of former prime minister Menachem Begin, which means the Golan Heights are like Tel Aviv or Holon,” he said.
There is concern in Israel that if the regime of Syrian President Bashar Assad is toppled, the country could fall into the hands of Islamic extremists or descend into sectarian warfare, destabilizing the region. Still, Israel has expressed empathy for Syrian citizens caught up in the vicious fighting.
Israeli officials have also expressed concern that the frontier region could turn into a lawless area like Egypt’s Sinai desert, where Islamic extremists have gained strength since the ouster last year of president Hosni Mubarak.