Updated 12:15 p.m. ET
BEIRUT Israeli warplanes struck areas in and around the Syrian capital Sunday, setting off a series of explosions as they targeted a shipment of highly accurate, Iranian-made guided missiles believed to be bound for Lebanon's Hezbollah militant group, officials and activists said.
The attack, the second in three days and the third this year, signaled a sharp escalation of Israel's involvement in Syria's bloody civil war. Syrian state media reported that Israeli missiles struck a military and scientific research center near Damascus and caused casualties.
Syria's government called the attacks against against its territory a "flagrant violation of international law" that has made the Middle East "more dangerous" and warned it has the right "to defend its people by all available means."
The generally muted response, read out by the information minister after an emergency government meeting, appeared to signal that Damascus did not want the situation to escalate.
Instead, it tried to use the strikes to taint the rebels, claiming the attacks were evidence of an alliance between Israel and Islamic extremist groups trying to overthrow President Bashar Assad.
The air raids pose a dilemma for a regime already battling a relentless rebellion at home. Failure to respond could make it look weak and open the door to more strikes. But any military retaliation against Israel would risk dragging the Jewish state and its powerful army into a broader conflict.
The tempo of the new strikes added a dangerous dynamic to the conflict, fueling concerns that events could spin out of control and spark a regional crisis.
Israel's military on Sunday deployed two batteries of its Iron Dome rocket defense system to the north of the country. It described the move as part of "ongoing situational assessments."
A senior Israeli official, who spoke on condition of anonymity in order to disclose information about a secret military operation to the media, confirmed that Israel launched an airstrike in the Syrian capital early Sunday but did not give more precise details about the location. The target was Fateh-110 missiles, which have precision guidance systems with better aim than anything Hezbollah is known to have in its arsenal, the official told The Associated Press.
The airstrikes come as Washington considers how to respond to indications that the Syrian regime may have used chemical weapons in its civil war. President Barack Obama has described the use of such weapons as a "red line," and the administration is weighing its options including possible military action.
Iran, a close ally of the Assad regime and Hezbollah, condemned the airstrikes, and a senior official hinted at a possible response not from Terhan, but rather its proxy, Hezbollah.
Gen. Masoud Jazayeri, assistant to the Iranian chief-of-staff, told Iran's state-run Arabic-language Al-Alam TV that Tehran "will not allow the enemy (Israel) to harm the security of the region" and that "the resistance will retaliate against the Israeli aggression against Syria."
Israel has said it wants to stay out of the Syrian war on its doorstep, but Prime Minister Benjamin Netanyahu has repeatedly stated the Jewish state would be prepared to take military action to prevent sophisticated weapons from flowing from Syria to Hezbollah or other extremist groups.
Israel and Hezbollah have a long history of enmity, and fought a punishing monthlong war in mid-2006. The militant group fired thousands of rockets at Israel, while Israeli warplanes destroyed large areas of southern and eastern Lebanon during a conflict that ended in stalemate.
Israel is especially concerned that Hezbollah will take advantage of the chaos in neighboring Syria and try to smuggle advanced weapons into Lebanon, particularly those that could hamper Israel's ability to operate in Lebanese skies.
Officials in Israel say they have identified several "game changing" weapons that would trigger military intervention in Syria: chemical weapons, long-range Scud B missiles, the Fateh-110s, land-to-sea Yakhont missiles and SA-17 anti-aircraft missiles.
Israeli officials believe that Iran and Hezbollah are stepping up their efforts to smuggle weapons because they think Assad's days are numbered. They also think the Syrian leader is cooperating because he is weak and he owes Hezbollah, which is understood to be sending men to fight alongside government troops, for its support.
The officials, who spoke on condition of anonymity because they were not authorized to brief the media, said Israel will continue to strike Syria if the smuggling attempts continue.
Syria's state news agency reported explosions at the Jamraya military and scientific research center near Damascus and said initial reports indicate they were the "result of Israeli missiles." It said there were casualties but did not give a number.