A mortar shell apparently fired from Syria struck the northern Golan Heights on Wednesday morning, causing neither injury nor damage, the army said.

The projectile, as with most others emanating from the war-torn country, appeared to be accidental spillover rather than an intentional attack on Israel, the Israel Defense Forces said in a statement.

Nevertheless, the Israeli army fired back into Syria, hitting “artillery positions belonging to the Syrian regime in the northern Syrian Golan Heights,” the military said.

The army would not elaborate on how Israel retaliated to the attack, whether it was by airstrike or artillery fire.

“The IDF will not tolerate any attempt to harm the sovereignty of the State of Israel or the security of its citizens,” the army said.

On Wednesday, Israel said it holds the Syrian regime responsible for all errant fire, regardless of the source. However, in the past, the army has also noted that it “will not hesitate to act against any opposition forces in Syria.”

The Syrian Observatory for Human Rights organization reported clashes between Syrian regime and Islamic State-affiliated rebel forces near the border, including artillery bombardments.

According to the group, fierce battles raged in both the city of Quneitra and in the town of Beit Jinn, located some 6 miles (10 kilometers) from the border with Israel.

In Beit Jinn, the Bashar Assad regime forces conducted “intense” shelling against the rebels, according to the Syrian Observatory. That was apparently the source of the shell that struck Israeli territory.

After repeated cases of accidental spillover striking Israeli territory in September, the vicious fighting in Syria has since largely stayed across the border.