BEIRUT (AP) _ 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 on their way to Lebanon's Hezbollah militant group, officials and activists said.

The attack, the second in three days, 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.

An intelligence official in the Middle East, 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, condemned the airstrikes but gave no other hints of a possible stronger response from Tehran.

Israel has said it wants to stay out of the Syrian war, 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 fought a monthlong war in mid-2006 that ended in a stalemate.

Syria's state news agency SANA reported that explosions went off at the Jamraya military and scientific research center near Damascus and said ``initial reports point to these explosions being a result of Israeli missiles.'' SANA said there were casualties but did not give a number.

Damascus-based activist Maath al-Shami said the strikes occurred around 3 a.m. ``Damascus shook. The explosion was very, very strong,'' said al-Shami adding that one of the attacks occurred near the capital's Qasioun mountain that overlooks Damascus.

He said the raid near Qasioun targeted a military position for the elite Republican Guards that is in charge of protecting Damascus, President Bashar Assad's seat of power.

Mohammed Saeed, another activist who lives in the Damascus suburb of Douma, said ``the explosions were so strong that earth shook under us.'' He said the smell of the fire caused by the air raid near Qasioun could be felt miles away.

There has been no official statement from the Syrian military.

The strikes put the Assad regime in a tricky position. If it fails to respond, it looks weak and leaves itself open to such airstrikes becoming a common occurrence. But if it retaliates militarily against Israel, it risks dragging the Jewish state and its powerful military into a broader conflict.

After the airstrikes overnight, Israel's military on Saturday deployed two batteries of its Iron Dome rocket defense system to the country's north. It described the move as part of ``ongoing situational assessments.''

The Iron Dome protects against short-range rockets. Hezbollah fired thousands of rockets at Israel during the 2006 war, while Israeli warplanes destroyed large areas of south Lebanon.

Amos Yadlin, a former head of Israel's military intelligence, said the strike is a signal to Syria's ally, Tehran, that Israel is serious about the red lines it has set.

``Syria is a very important part in the front that Iran has built. Iran is testing Israel and the U.S. determination in the facing of red lines and what it sees is in clarifies to it that at least some of the players, when they define red lines and they are crossed, take it seriously,'' he told Army Radio.

In Tehran, Iran's Foreign Ministry spokesman Ramin Mehmanparast condemned an Israeli airstrike against Syria and urged countries in the region to remain united against Israel, according to the semiofficial Fars news agency. The brief statement gave no details.

The Fateh-110, or Conqueror, is a short-range ballistic missile developed by Iran and first put into service in 2002. The Islamic Republic unveiled an upgraded version in 2012 that improved the weapon's accuracy and increased its range to 300 kilometers (185 miles).

Iranian Defense Minister Gen. Ahmad Vahidi said at the time that the solid-fueled missile could strike with pin-point precision, making it the most accurate weapon of its kind in Iran's arsenal.

An airstrike in January also targeted weapons apparently bound for Hezbollah, Israeli and U.S. officials have said. The White House had no immediate comment on Sunday's reported missile strikes.

The Britain-based Syrian Observatory for Human Rights, an activist group, also reported large explosions in the area of Jamraya, a military and scientific research facility northwest of Damascus, about 15 kilometers (10 miles) from the Lebanese border.

Hezbollah's al-Manar TV said the research center in Jamraya was not hit. It added that an army supply center was targeted by the strike. It quoted unnamed Syrian security officials as saying that three sites including military barracks, arms depots and air defense center were targeted by the strike.

The station aired footage of what it said was a facility in Jamraya that was hit in the airstrike. It showed a heavily damaged building as well as what appeared to be a chicken farm with some chickens pecking around in debris scattered with dead birds.

The raid appeared to have taken place next to a major road that was filled with debris, and shell casings were strewn on the ground. A blue street sign on the side of the road referred to the direction of the Lebanon border and the Syrian town of Zabadani near the frontier.

Lebanon's Al-Mayadeen TV, that has several reporters around Syria, said one of the strikes targeted a military position in the village of Saboura, west of Damascus and about 10 kilometers (six miles) from the Lebanon border.

An amateur video said to be shot early Sunday in the Damascus area showed fire lighting up the night sky. The video appeared genuine and corresponded to other AP reporting.

Uzi Rubin, a missile expert and former Defense Ministry official, told the AP that if the target were Fateh-110 missiles as reported then it is a game changer as they put almost all Israel in range and can accurately hit targets.

Rubin emphasized that he was speaking as a rocket expert and had no details on reported strikes.

``If fired from southern Lebanon they can reach Tel Aviv and even (the southern city of) Beersheba.'' He said the rockets are much five times more accurate than the scud missiles that Hezbollah has fired in the past. ``It is a game changer because they are a threat to Israel's infrastructure and military installations,'' he said.

Israel's first airstrike in Syria, in January, also struck Jamraya.

At the time, a U.S. official said Israel targeted trucks next to the research center that carried SA-17 anti-aircraft missiles. The strikes hit both the trucks and the research facility, the official said. The Syrian military didn't confirm a hit on a weapons shipment at the time, saying only that Israeli warplanes bombed the research center.

Israeli lawmaker Shaul Mofaz, a former defense minister and a former chief of staff, declined to confirm the airstrike but said Israel is concerned about weapons falling into the hands of the Islamic militant group amid the chaos of Syria's civil war.

``We must remember that the Syrian system is falling apart and Iran and Hezbollah are involved up to their necks in Syria helping Bashar Assad,'' he told Israel Radio. ``There are dangers of weapons trickling to the Hezbollah and chemical weapons trickling to irresponsible groups like al-Qaida.''