Iranian forces based in Syria fired approximately 20 rockets toward Israeli positions in the Golan Heights, triggering a retaliatory bombardment that rocked Syria's capital late into the night Wednesday.
The Israel Defense Forces (IDF) said its Iron Dome missile defense system had intercepted "some" of the incoming rockets. No injuries were reported.
Damascus shook with the sounds of explosions just before dawn, and firing by Syrian air defenses over the city was heard throughout the night. Syria's state news agency SANA quoted a Syrian military official as saying Israeli missiles hit air defense positions, radar stations and a weapons warehouse, but claiming most incoming rockets were intercepted.
Lt. Col. Jonathan Conricus, an Israeli military spokesman, said earlier that Iran's Al Quds force fired the rockets at several Israeli bases, though he would not say how Israel determined the Iranian involvement. The incoming attack set off air raid sirens in the Golan Heights, which were captured from Syria in the 1967 war.
Israel "views this Iranian attack very severely," Conricus told reporters. He said Israel had responded, but did not provide details.
"This event is not over," he added.
In a statement to Fox News, the IDF asked residents of the Golan Heights to remain in special "safety zones" for the time being.
Syria's state media said Syrian air defenses had intercepted "hostile Israeli missiles" early Thursday that were fired over southwestern Damascus. Hours later, state-run Al-Ikhbariya TV broadcast a live feed of Syrian air defenses firing into the sky above the capital, and loud explosions and air defense firing were heard through the night.
Syrian activists reported Israeli airstrikes hitting targets near Damascus. One video posted online showed a large explosion and shrapnel flying in the air. Residents reported loud sounds that rocked their buildings. It was not immediately clear what was hit.
An Israeli army spokesman, Avichay Adraee, said on Twitter that Israel was "acting against Iranian targets inside Syria," a rare admission by an Israeli official.
"Any Syrian involvement against this move will be faced with extreme seriousness," Adraee added.
Al-Ikhbariya TV said Israel also targeted military posts in southern Suweida province, including an air base, and struck near Homs in central Syria. The state TV station said the attacks were foiled.
Syrian media earlier said the hostilities began with Israeli fire at Syrian positions in southern Syria from across the border. Pro-Syrian media said Syrian missiles then fired at Israeli forces. One TV station, Beirut-based Al-Mayadeen, said at least 50 missiles were fired from Syria at Israeli forces in the Golan Heights. Al-Ikhbariya TV said missiles targeted 10 Israeli positions.
Syrian media said it was the first time in years that Syrians had fired at Israeli forces in the Golan Heights.
Israel has been on heightened alert in recent days, anticipating a possible Iranian retaliation for a series of deadly strikes on its military positions in Syria.
Syrian state media said Israel struck a military outpost on Tuesday near the capital of Damascus. The Britain-based Syrian Observatory for Human Rights said the missiles targeted depots and rocket launchers that likely belonged to Iran's elite Revolutionary Guard in Kisweh, killing at least 15 people, eight of them Iranians.
Just before midnight Wednesday, Syria state news agency reported that rockets suspected to be coming from Israel hit southern Syria's Quneitra province. Activists said it was artillery fire from Israeli positions in the Golan Heights. There were no reports of any deaths.
Tensions between Israel and Iran are high over Iran's efforts to expand its military presence in Syria, where it is a key ally of President Bashar Assad. Repeated airstrikes attributed to Israel have killed Iranian fighters and prompted threats of reprisal from Tehran. Meantime, President Donald Trump's announcement Tuesday that the U.S. would withdraw from the 2015 nuclear deal with Iran has triggered uncertainty and threatened to spark more unrest in the Middle East.
"This just further shows that the Iranian regime cannot be trusted," White House press secretary Sarah Sanders told Fox News' "The Story." "Israel absolutely has a sovereign right to defend itself and we support them in whatever efforts they have in order to defend themselves. But again, I think this activity and this action is just further demonstration that the Iranian regime cannot be trusted and another good reminder that the president made the right decision to get out of the Iran deal."
Fox News' Martha MacCallum and The Associated Press contributed to this report.