The Israeli Air Force struck off an Islamic State-affiliated group in Syria, killing four of its members, hours after the group fired on Israeli soldiers across the border.

The Israel Defence Forces confirmed that its soldiers were conducting an operation in the Golan Heights in which they passed the security fence with Syria while remaining in Israeli territory. They then came under attack with machine gun fire. The soldiers returned fire.

No injuries to Israeli soldiers were reported.

It is not known if the mortar shells landed in Israeli or Syrian territory.

The Air Force launched a retaliatory attack within minutes of the gun fire. Pilots reported the death of the four ISIS cell members.

It is reportedly the first clash between Israel and the Islamic State. Most previous attacks on Israel from Syria have been accidental spillover from the internal fighting. The IDF has responded to those with return fire.

“The army will not tolerate any attack on its sovereignty and will respond severely to any attempt to violate it,” the army said in a statement.

The mortar and gun fire toward Israel comes amid renewed fighting in the area between rebel forces and the army of Syrian President Bashar Assad in a more than five-year civil war.