BEIRUT (AP) -- Syria's military said Israel struck a military installation southwest of Damascus International Airport before dawn Thursday, setting off a series of explosions and raising tensions further between the two neighbors.
Apparently seeking to interrupt weapons transfers to the Hezbollah group in Lebanon, Israel has struck inside Syria with increasing frequency in recent weeks, making the war-torn country a proxy theater for Israel's wider war with Iran.
The increasing tempo of attacks risks inflaming a highly combustible situation drawing in Israel, Syria and the Iranian-backed Hezbollah, a staunch ally of President Bashar Assad's government with thousands of fighters in Syria. Israel's military said later Thursday that its Patriot Missile Defense system intercepted an incoming projectile from Syria over the Golan Heights.
An Israeli defense official said the Patriot hit a drone, and the military is checking if it was a Russian aircraft that entered the Israeli side by mistake or if it was Syrian. He spoke on condition of anonymity in line with protocol.
Both the Syrian government and Hezbollah, however, are mired in the country's 6-year-old civil war and are unlikely to carry out any retaliation that may ignite a bigger conflagration with Israel.
"Iran and Hezbollah are overstretched, and it's not clear they can afford to gamble with a direct showdown with Israel now," said Maha Yahya, director of the Carnegie Middle East Center. "Iran knows no matter how powerful they've become, they can't be fighting on two fronts at the same time."
Israeli Minister of Intelligence Yisrael Katz would not comment directly on the incident but said any similar strike would be in line with established policy to interrupt weapons transfers.
"It absolutely matches our declared policy, a policy that we also implement," Katz told Israel's Army Radio.
Just before the apparent Israeli missile strike, at least three cargo jets from Iran probably landed at the Damascus airport, said Ian Petchenik, a spokesman for the flight-tracking website FlightRadar24. They include an Il-76 flown by the Iranian cargo company Pouya Air that "was last tracked over Iraq headed towards Damascus," he said.
It's unknown what they were carrying. Passenger flights and civilian cargo jets continue flying into Damascus, although there's suspicion that some commercial flights serve as cover for weapons transfers from Iran.
The Washington-based Foundation for Defense of Democracies, a right-leaning think tank that has criticized the nuclear deal Iran struck with world powers, has said Pouya Air is the latest name for a long-sanctioned airline. It also has accused Pouya Air of funneling arms from Iran into Yemen's capital of Sanaa to supply Shiite rebels there.
Emanuele Ottolenghi, a senior fellow at the foundation, said he tracked a fourth cargo flight from Iran to Syria on Wednesday night, an Airbus A300 operated by Mahan Air, which is suspected of ties to Iran's paramilitary Revolutionary Guard. He also called one of the cargo flights, a Qeshm Fars Air Boeing 747, especially suspicious because the airline stopped operating in 2013, only to resume flights to Damascus three weeks ago.
"We don't know for sure, but let's say that we can fairly safely assume that the weaponry and fighters reach Damascus through these daily flights," Ottolenghi told The Associated Press.
The explosions near Damascus reverberated across the capital, seat of Assad's power.
Syria's state-run SANA news agency said Israel had fired several missiles from inside the occupied Golan Heights, 60 kilometers (37 miles) south of Damascus, striking a military installation southwest of the airport that serves both military and civilian flights. It reported damage but no casualties.
"The buildings shook from the force of the blast," said a media activist who goes by Salam al-Ghoutawi of the Ghouta Media Center in the opposition-held northeastern suburbs, about 15 kilometers (9 miles) from the airport. He said he heard the roar of jets in the distance.
Explosions were silhouetted against the night sky in a video published by the center. Debris was seen flying out as the explosions illuminated a sizeable cloud nearby.
Hezbollah's al-Manar media station reported a blast at fuel tanks and a warehouse next to the airport, which is 25 kilometers (16 miles) east of central Damascus.
The Syrian military said in a statement the attack sought to "raise the morale of terrorist groups" the government maintains are fighting Assad's forces. It made no mention of whether it would respond.
Israel is widely believed to have carried out airstrikes in recent years on advanced weapons systems in Syria - including Russian-made anti-aircraft missiles and Iranian-made missiles - as well as on Hezbollah positions. It rarely comments on such operations.
Last month, Syria fired missiles at Israeli jets after they struck targets in Syria, in a rare military exchange between the two adversaries.
Hezbollah is an avowed enemy of Israel, and the two sides fought a monthlong war in 2006. Tensions between them along the Lebanon-Israel border have risen in recent weeks, with each side warning of a much more serious confrontation. Some Israeli officials have also recently been threatening grave damage to the Lebanese civilian infrastructure in case of a new conflict with Hezbollah, apparently in hopes the country can somehow rein in the militia.
Yahya, the analyst, said Israel is increasingly worried about the potential arsenal that Hezbollah's could acquire and the weapons already available in Syria.
"Most likely they see a window of opportunity where their intervention can degrade Hezbollah's military power," she said.
The conflict in Syria, which pits Assad and his regional allies against local and foreign opposition forces, has killed more than 400,000 people since it began in 2011. The civil war is further complicated by militant factions such as al-Qaida's affiliate in Syria and the even more powerful Islamic State group, which in 2014 seized a large chunk of territory but lately has been losing ground in the face of a campaign by a U.S.-led international coalition.
Russia, another key Assad ally, denounced what it called an act of "aggression" against Syria. Foreign Ministry spokeswoman Maria Zakharova did not directly blame Israel for Thursday's explosion, but she cited Syrian media as saying Israel was responsible.
In other developments, at least 19 people were killed in air raids across rebel-held Idlib province in the northwest. Some appeared to target ambulances and medical centers.
The Civil Defense, a search-and-rescue organization, said four medical staff were killed in an attack on a university hospital in the town of Deir Sharqi, and four paramedics or ambulance operators died in an airstrike on an ambulance services in another town, Maarzita.
The Britain-based Syrian Observatory for Human Rights said 19 civilians, including nine children, were killed around the province. The Civil Defense reported the same overall death toll.
The activists believe Russia or the Syrian government launched the raids. U.S. jets also are known to strike in Idlib province, targeting al-Qaida-linked fighters.
Associated Press writers Sarah El Deeb in Beirut, Ian Deitch in Jerusalem, Jon Gambrell in Dubai, United Arab Emirates, and Albert Aji in Damascus contributed.