BEIRUT — Four huge explosions just west of Damascus shook the ground across the Syrian capital early Sunday, sending fiery mushroom-shaped clouds towering over the landmark Mount Qasioun and brightening the night sky in a demonstration of firepower larger than anything the residents of the capital have witnessed during more than two years of civil war.
The Syrian government immediately blamed Israel for the explosions, which seemed far beyond the capabilities of the rebel arsenal. Israeli officials refused to confirm their forces carried out the strikes, which the Syrian deputy foreign minister called ‘‘an act of war.’’
With much still unexplained about the effects and motivations of the attack, questions transfixed the region, which has lived in fear that the Syrian war will lead to a wider conflagration.
It was unclear whether Israel — if it carried out the strikes — sought to intervene in Syria’s civil conflict or was expanding its campaign to prevent the Syrian government from transferring weapons to Hezbollah, the militant Shi’ite organization in Lebanon that is one of Israel’s most dangerous foes.
While the Israeli government had no comment on the operation, the Associated Press quoted a senior Israeli official as saying Sunday’s raid and another one 48 hours earlier were Israeli strikes against shipments of Fateh-110 missiles bound for Hezbollah. The Iranian-made guided missiles can fly deep into Israel and accurately deliver half-ton bombs. The official spoke on condition of anonymity because he was discussing a covert operation.
The attacks could end up providing a psychological and perhaps military assist to the Syrian rebels, who over the last several weeks have faced losses in a series of government offensives around Damascus and the city of Homs to the north.
For the rebels, any benefit from the damage to crucial military structures from the attacks — said by opposition activists to have hit bases of elite troops as well as weapons stores — could be offset by political complications if the attack is linked to Israel, their country’s longtime enemy.
Israel deployed two of its Iron Dome missile-defense batteries in northern cities, and Prime Minister Benjamin Netanyahu avoided any mention of the developments in Syria in his remarks at the start of the weekly Cabinet meeting Sunday. He did, however, delay by two hours an evening departure for China so he could convene his security Cabinet.
If it was carried out by Israel, the Syrian operation would be Israel’s third in Syria this year. A US official said the more limited raid early on Friday at Damascus International Airport was meant to destroy weapons being sent from Iran to Hezbollah, an aim similar to that of an Israeli strike in January.
But the explosions on Sunday appeared to be of far greater magnitude and potentially broader political and military significance.
Within hours of the explosions, the rebel Damascus Military Council issued a statement calling on all fighters in the area to work together, put aside rivalries, and mount focused attacks on government forces that so far have kept a solid hold on Damascus, the capital.
Still, military analysts said Sunday’s attacks by themselves were not likely to tip the balance between the rebels and the Syrian president, Bashar Assad.
And Louay Mekdad, a spokesman for the Supreme Military Council, which is considered the United States’ best option for an ally among the rebels, discounted claims by some rebel groups that they would take advantage of the airstrikes to escalate their attacks.
Video posted online showed multiple explosions hitting the area west of the Syrian capital, which is home to several crucial military installations. According to residents in the area and Syrian opposition groups, the attacks struck bases of the army’s elite fighting units as well as a research center that US officials have said is the country’s main facility for chemical weapons development.
Not all those assertions were confirmed by the Syrian government, which said only that the research center in Jamraya had been hit. Witnesses reported other strikes near Mount Qasioun and the town of Saboura.
Syrian state television said the explosions confirmed what the government has been contending all along: that the rebels are part of a US-Israeli conspiracy to target Assad for his support of Palestinians and opposition to Western policies in the Middle East.
While being seen as allies of Israel could tarnish their reputation in Syrian eyes, the rebels could also point to the strikes as proof of their government’s hypocrisy. A frequent refrain among fighters and activists has been that while the government’s security forces and military failed to prevent the Israeli strikes — and for that matter have not clashed with Israel since 1973 — they have killed tens of thousands of Syrians and jailed many more in order to hold onto power.
Some rebels and activists say openly they consider Assad a far higher-priority target than Israel, while making clear that they do not embrace Israel. The main exile Syrian opposition coalition walked that line carefully in a statement issued after the bombings, blaming the government for allowing attacks by ‘‘external occupying forces.’’
Iran’s defense minister, General Ahmad Vahidi, traveling inside the country with President Mahmoud Ahmadinejad, accused the United States of ‘‘giving the green light’’ for the airstrikes.