A Syrian mortar shell exploded on the Golan Heights Thursday, setting off air-raid sirens. The shell was likely stray cross-border fire due to intense battles raging between the Assad regime’s military and rebels near the border. There were no injuries or damage in the incident.In response, the IDF fired a guided Tamuz missile at a Syrian Army post. In a statement, the IDF said it holds the Syrian Army responsible for all cross-border fire into Israel. It was not immediately clear whether Syrian casualties resulted from the missile strike.Rebel groups and Syrian Army forces loyal to the regime of President Bashar Assad have been locked in fierce battles in recent weeks over the Quneitra crossing on the Syria-Israel border. Stray fire has spilled over into Israel on a number of occasions.Two mortar shells from Syria fell in the Golan Heights on Monday.The IDF continues to closely monitor developments across the border. Rebel forces are still holding 44 UN peacekeepers from Fiji hostage. Last week, Islamist fighters overran the Quneitra border crossing and opened fire on the UN blue helmets, who are part of the UN Disengagement Observers Force of peacekeepers that has patrolled the cease-fire line for 40 years. A group of 32 Philippine UNDOF soldiers managed to flee from capture on Saturday after they received backup from other UN forces.In June, several Syrian soldiers were killed and 10 were injured in IDF strikes on Syrian military targets, launched in response to an earlier deliberate cross-border missile attack that killed a 14-year-old Arab Israeli. The targets included Syrian command posts and firing positions, the IDF said. Israeli jets and Tamuz surface-to-surface missiles struck nine targets belonging to the Syrian military.Reuters contributed to this report.