Israel's weekend airstrike on a military complex near the Syrian capital of Damascus killed at least 42 Syrian soldiers, a group of anti-regime activists said Monday, citing information from military hospitals.
The Syrian government has not released a death toll, but Syrian state media have reported casualties in Sunday's predawn airstrike, Israel's third into Syria so far this year.
The Britain-based Syrian Observatory for Human Rights said about 150 soldiers are normally stationed in the area that was targeted, but that it was not clear how many were there at the time of the strike.
Israel's government has not formally confirmed involvement in strikes on Syria. However, Israeli officials said the strikes were meant to prevent advanced Iranian weapons from reaching Lebanon's Hezbollah militia, an ally of Syria and foe of Israel.
The officials spoke on condition of anonymity because they were not authorized to discuss covert military operations.
Israel on Monday signaled a return to "business as usual," with Prime Minister Benjamin Netanyahu arriving in China for a scheduled visit,
Syria and its patron Iran have hinted at possible retribution over the strikes, though the rhetoric in official statements has been relatively muted.
Iranian Foreign Minister Ali Akbar Salehi warned Monday that Israel was "playing with fire," but gave no other suggestions of possible consequences, according to the official Islamic Republic News Agency.
Syria's government called the attacks a "flagrant violation of international law" that has made the Middle East "more dangerous." It also claimed the Israeli strikes proved Israel's links to rebel groups trying to overthrow Assad's regime.
Israeli officials have indicated they will keep trying to block what they see as an effort by Iran to send sophisticated weapons to Lebanon's Hezbollah militia ahead of a possible collapse of Syrian President Bashar Assad's regime.
Israel has repeatedly threatened to intervene in the Syrian civil war to stop the transfer of what it calls "game-changing" weapons to Hezbollah, a Syrian-backed group that battled Israel to a stalemate during a month-long war in 2006.
Since carrying out a lone airstrike in January that reportedly destroyed a shipment of anti-aircraft missiles headed to Hezbollah, Israel had largely stayed on the sidelines. That changed this weekend with the pair of airstrikes, including an attack near a sprawling military complex close to Damascus early Sunday that set off a series of powerful explosions.
A senior Israeli official said both airstrikes targeted shipments of Fateh-110 missiles bound for Hezbollah. The Iranian-made guided missiles can fly deep into Israel and deliver powerful half-ton bombs with pinpoint accuracy. The official spoke on condition of anonymity because he was discussing a covert military operation.