The three tanks entered the DMZ on Saturday and Israel lodged a complaint with the peacekeepers, an Israeli military spokeswoman said, speaking on condition of anonymity in line with military protocol. She did not elaborate on what the tanks were doing.
The Israeli news site Ynet said the tanks and two armored personnel carriers drove a few miles away from Israeli military positions.
Israel captured the Golan Heights from Syria in the 1967 Mideast war. It later annexed the strategic territory overlooking northern Israel in a move that is not recognized internationally. Before 1967, Syria used the highlands to shell Israeli villages and farms.
The DMZ, which is about 3.5 miles at its widest and 20 yards at its narrowest, was created after the 1973 war in which Syria tried to retake the 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 was no immediate comment from Syria.
Israel and Syria have been bitter enemies for decades and have fought several wars but the border has been mostly quiet for years.
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.
Israeli officials have also expressed concern that the frontier region could turn into a lawless area like Egypt's Sinai desert, where Islamic militants have gained strength since the ouster last year of Egyptian President Hosni Mubarak.