Israel says it has hit dozens of targets in Syria of the Syrian government and allied Iranian forces.
Syria's state media released images of what they say are destroyed houses near Damascus. Photo: AFP
The Israeli military says the "wide-scale strikes" responded to rockets fired by an Iranian unit into Israel.
Syria says two civilians died and that Syrian air defences shot down most of the missiles over Damascus. Other reports say the death toll was higher.
Local reports said loud explosions were heard in the capital. Pictures on social media showed a number of fires.
On Tuesday morning, the Israeli military said it had intercepted four rockets fired from Syria towards northern Israel. It said the rockets did not hit the ground.
Israel is believed to have carried out hundreds of strikes in Syria since civil war broke out there in 2011, to try to prevent Iran gaining a foothold.
What did Israel say?
Early on Wednesday, Israel Defense Forces (IDF) tweeted that the strikes targeted positions of Iran's Quds Force and Syria's armed forces.
"During our strike of Iranian & Syrian terror targets, a Syrian air defence missile was fired despite clear warnings to refrain from such fire. As a result, a number of Syrian aerial defence batteries were destroyed," the IDF said.
The Israeli military also said it held "the Syrian regime responsible for the actions that take place in Syrian territory and warn them against allowing further attacks against Israel".
Iran's Quds Force, which answers directly to Iran's Supreme Leader, Ayatollah Ali Khamanei, is the external operations wing of the Islamic Revolution Guard Corps (IRGC).
Israel did not target the Russian-made advanced S-300 surface-to-air missile systems deployed near the positions of Russian troops, Israeli media report.
Russia, whose forces have helped turned the tide of Syria's civil war in favour of President Bashar al-Assad, condemned the Israeli strikes.
What did Syria say?
Syria's state news agency Sana said that the country's "air defence confronted the heavy attack and intercepted the hostile missiles".
It said that Syria destroyed "most" of the Israeli missiles.
The news agency added that the strikes on Syrian territory were carried out from "Lebanese and Palestinian territories".
Israel has a number of times hit targets inside Syria from war planes in Lebanese airspace.
Danny Makki, a British-Syrian journalist based in Damascus, posted footage of what he said he believed were Israeli missiles hitting targets south of Damascus.
Syria said two civilians were killed in the Israeli strikes.
Meanwhile, a UK-based monitoring group, the Syrian Observatory for Human Rights (SOHR), said that 11 fighters, including seven foreigners, died.
The SOHR said that the Israeli missiles hit the sites in and around Damascus in Kiswa, Saasaa, Mezzeh military airport, Jdaidat Artouz, Qudsaya and Sahnaya.
And what about Iran?
The Iranian authorities have so far made no public comment.
- BBC