By Frederik Pleitgen and Sara Sidner
A Syrian official called an attack Sunday on the nation's military research facility a "declaration of war" by Israel.
In an interview with CNN, Deputy Foreign Minister Faisal al Mekdad said the attack represented an alliance between Islamic terrorists and Israel.
He added that Syria would retaliate against Israel in its own time and way.
Early Sunday morning, a series of massive explosions illuminated the predawn sky in Damascus, prompting more claims that Israel has launched attacks into the war-torn country.
Syria accused Israel of firing rockets into the Damascus suburb of Jamraya, striking the research center, Syrian state-run TV reported. The report claimed that the rocket attack on the research center aided rebels, who have been battling government forces in the region.
The Israeli military would not confirm nor deny the Syrian TV claim that Israel had launched rockets.
"We do not comment on these reports at all," an Israeli military spokesperson said.
An Israeli Army official told CNN that two rocket interception batteries have been deployed to northern Israel.
The report comes shortly after U.S. officials first told CNN that the United States believes Israel conducted an airstrike against Syria. Two U.S. officials told CNN on Friday that Israel apparently launched an airstrike into Syria on Thursday or Friday. Based on initial information, the United States does not believe Israeli warplanes entered Syrian airspace to conduct the strike.
The Israeli military did not comment on the U.S. claim of an airstrike. But Israel has long said it would target any transfer of weapons to Hezbollah or other terrorist groups, as well as at any effort to smuggle Syrian weapons into Lebanon that could threaten Israel.
"We are watching everything when it comes to the movement of these types of weapons. We have the means to do that," a senior Israeli defense official told CNN's Sara Sidner on Sunday. The official is not authorized to speak to the media.
Shaul Mofaz, a lawmaker with Israel's Knesset, told Israeli Army Radio that Israel isn't meddling with Syria's civil war. But Israel must protect itself from Lebanese militants, he said.
"For Israel, it is very important that the front group for Iran, which is in Lebanon, needs to be stopped," Mofaz said.
"Everything that goes into the hands of Hezbollah is not directly related to the rebels. Israel never interfered in the past or today in their actions.
Nevertheless, I need to say that Hezbollah is deeply involved up to its neck in what is happening in Syria. Hezbollah helps the Iranians navigate against the rebels."
Neither Hezbollah nor the Lebanese government commented immediately after Sunday's claims.
Syria: Israel has targeted the defense facility before
Sunday's report is the second claim by Syria this year of a strike against the government defense research facility,
In January, reports surfaced that Israeli warplanes targeted the Jamraya research facility. The Syrian government has said that airstrike killed two workers and injured five others.
A U.S. official told CNN at the time the Syrian claims were false. The official said Israeli fighter jets targeted a Syrian government convoy carrying surface-to-air missiles bound for Hezbollah. But Syria denied there were such shipments.
Lebanon reports Israeli warplanes overhead
Claims of Israeli foreign presence was not limited to Syria; the Lebanese army said Israel flew warplanes over Lebanon on Thursday, Friday and Saturday.
Lebanese President Gen. Michel Sleiman condemned the violations as "an attempt to shaken Lebanese stability," the state-run National News Agency reported Saturday.
The Israeli military had no comment on the Lebanese claim. But an Israeli defense source said, "We will do whatever is necessary to stop the transfer of weapons from Syria to terrorist organizations. We have done it in the past, and we will do it if necessary the future."
Sectarian violence continues
The latest report of rocket attacks comes as sectarian violence erupted in northwestern Syria. Three consecutive days of killing by mostly Alawite forces have left hundreds of predominantly Sunni residents dead, opposition groups said Saturday.
State media have said their forces were seeking only to clear the area of "terrorists," the term they have routinely used when referring to rebel forces.
But the U.S. State Department said it was "appalled by horrific reports that more than 100 people were killed May 2" in Beyda, a suburb of Baniyas.
Several opposition groups said largely Alawite regime forces used tanks, battleships and missile launchers to target largely Sunni neighborhoods in and around the coastal city of Baniyas.
Government forces killed at least 200 people on Friday and Saturday in Baniyas and its suburbs, the opposition Local Coordination Committees said Saturday.
But reliable information has been difficult to obtain because government forces controlled access to the village, the LCC said.
A graphic video posted by activists who said it was shot in the Ras al-Nabaa neighborhood showed people, including an infant, lying lifeless on the ground. Many bore what appeared to be bullet wounds, and some appeared burned.
CNN has not been able to confirm the video's authenticity, as access to Syrian war zones has been severely limited by the government.
State-run Syrian TV reported that government troops and the National Defense militia - an armed Alawite group loyal to the government, "have cleaned the area from armed terrorists" after "they burned civilians' homes and terrorized the population." The report was supported by interviews with members of the Syrian army.
U.S. President Barack Obama told reporters on Friday that he did not foresee a scenario of "American boots on the ground in Syria" that would be good for that country or the region. Obama said other leaders in the region want to see al-Assad out of power.
CNN's Frederik Pleitgen reported from Damascus; Sara Sidner reported from Jerusalem. CNN's Holly Yan, Barbara Starr and Saad Abedine contributed to this report