The IDF fired an anti-tank missile as a warning shot toward Syrian forces near the border on Sunday afternoon, after Syrian troops fired a mortar shell that reportedly landed on an unmanned army post in the eastern Golan Heights. Israel Radio said Syrian troops also directed automatic weapons fire at Israeli troops, but the army did not confirm this.

The IDF fire into Syria was the first such incident since the 1973 Yom Kippur War.

The missile fired by the IDF, said by some sources to be a Tammuz anti-tank missile, was fired as a warning directly adjacent to a Syrian mortar battery.

IDF spokesman Brig. Gen. Yoav Mordechai said that Israeli security forces targeted a mortar squad operating near the Syrian army position that had apparently fired the mortar into the Golan, and that the IDF estimated there were no casualties on the Syrian side.

“We have no interest in getting in between the rebels and the Syrian army, but to defend the Golan Heights from stray fire,” Mordechai said.

Israel also conveyed a message to Syria that it would respond to any further spillover of fighting into Israel with return fire, Israel Radio reported.

No injuries or damage were reported from the mortar shell. The IDF said that the shell, which came from the direction of the Syrian village of Bir al-Ajami, was believed to be an errant shot from fighting between the Syrian army and rebel forces.

Israel filed an official complaint with the UN observer forces stationed along the demilitarized zone between Israel and Syria, and warned against further fire from inside Syria.

“More fire will result in a swift reaction,” the IDF said.

UN Secretary-General Ban Ki-moon confirmed in a statement from his New York office that the shelling was reported in the UN-monitored zone between Israel and Syria, but that no injuries to civilians or UN personnel were reported.

Ban called “for the utmost restraint” and urged Syria and Israel to uphold their ceasefire agreement and halt any exchange of fire.

On Sunday morning, Prime Minister Benjamin Netanyahu said Israel was “closely monitoring what is happening on our border with Syria and… we are ready for any development.”

Last week, three mortar shells from Syria fell in and around Moshav Alonei Habashan in the Golan, but caused no damage or injuries.

The IDF has been kept on high alert since November 3, when three Syrian tanks strayed into the demilitarized zone separating the two borders, leading Israel to lodge an official complaint with UN peacekeepers stationed in the DMZ.

Israel has long feared Syrian conflict spillover into the Golan. Last Monday, an army jeep was hit by a stray bullet from Syrian territory, just days after top IDF brass toured the region.

In September a number of mortar shells fired by regime forces landed in the north of the Golan Heights, and in another incident Syrian soldiers entered the DMZ.