At least two Syrian soldiers were reported injured Monday by an Israeli tank shell, fired deliberately at a mobile Syrian Army mortar battery that had just accidentally fired a mortar shell into Israeli territory in the Golan Heights.

Israeli TV stations showed what they said was footage of a Syrian ambulance evacuating the injured soldiers.

The Syrian casualties were believed to be the first such cases since the 1973 Yom Kippur War.

Israeli media reported that the decision to fire directly back at the Syrian troops was approved by the IDF’s Chief of the General Staff, Lt.-Gen. Benny Gantz.

TV news broadcasts reported Monday night that Syrian officials had made clear, via third parties, that they had “got the message” and would seek to avoid further such erroneous fire. Israeli military sources said the IDF remained on alert nonetheless, and would respond again at the sources of any further fire.

On Sunday, when a mortar fired from the same area fell inside Israeli territory, the IDF fired a high-precision Tammuz anti-tank missile toward the Syrian mortar battery, but deliberately aimed adjacent to the Syrian troops, hoping that this would constitute sufficient warning to put an end to the errant mortar fire. When Monday’s mortar fall demonstrated that the warning had not been registered, the decision was taken to fire back directly at the source of Syrian fire, Israeli military sources said.

The mortar shell that sparked Monday’s incident landed near Tel Hazeka in the Golan Heights.

Israeli media reports indicated that the target hit by the retaliatory Israeli tank fire was a Soviet-made D-30 howitzer piece manned by forces loyal to President Bashar Assad.

Israeli military officials still largely believe that the intermittent mortar fire into Israel from Syria in the last few days is a spillover from intense fighting near the frontier between Assad’s army and rebel forces, and not an overt attempt to hit the Jewish state and draw Israel into the conflict. Notably, Syrian state media has not reported on the cross-border incidents of recent days.

Israeli media said the Syrian troops are targeting rebel forces in a village in the Golan Heights Demilitarized Zone called Bir Ajam, and errant fire has led to shells falling inside Israel.

One senior Israeli official said Monday, however, that Israel is starting to question that assessment. “We thought it was spillover, but today we’re not sure,” said the official, speaking on condition of anonymity because the issue is still being debated among intelligence commanders.

The Syrian Observatory for Human Rights confirmed that Syrian rebels and government forces battled in Bir Ajam on Monday afternoon. According to the report, Bir Ajam was hit by mortar shells and there were casualties on both sides.

Clashes between government forces and Syrian rebels continued into the late afternoon, and three rebel fighters were killed, according to the British-based opposition Syrian Observatory.

Sunday’s incident, in which the Israel Defense Forces fired an anti-tank missile close to Syrian forces as a warning, followed an incident last week in which a shell fell inside an Israeli moshav, Alonai Habashan, but failed to explode; residents said the consequences could have been disastrous had it done so.

“We have no interest in getting in between the rebels and the Syrian army, but rather to defend the Golan Heights from stray fire,” IDF spokesman Brig. Gen. Yoav Mordechai said on Sunday.

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

Israel also 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.

In all last week, three mortar shells from Syria fell in and around Moshav Alonei Habashan, 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.

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.

The Associated Press contributed to this report.