Three Syrian tanks entered the demilitarised zone in the Golan Heights between Israel and Syria on Saturday, an Israeli military spokeswoman said.
"The Israeli Defense Forces have filed a complaint with the U.N. (peacekeeping) force in the area," the spokeswoman said. She had no further information on what the tanks were doing.
Israeli media said the tanks were involved in fighting in the Syrian village of Beer Ajam against rebels trying to overthrow President Bashar al-Assad.
Israel is technically at war with Syria, but it has generally taken a cautious line on the uprising in its Arab neighbour.
Errant Syrian mortars bombs landed in Israel in September, spurring Israel to lodge a similar complaint with the United Nations observer force that monitors a long-standing, de facto truce between the two countries.
Israel captured the Golan Heights, a strategic plateau, from Syria during a 1967 Middle East war. It later annexed it in 1981 in a move not recognised internationally.
In Washington, the White House had no immediate comment.