Syria and Israel engaged in the most serious incident between the two countries since the outbreak of the Syrian civil war six years ago overnight on Thursday, as Israeli Air Force planes struck several targets in Syria.

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In response, the Assad regime deployed air defense systems and fired a number of missiles toward Israeli jets. The Israeli army said that none of the missiles struck the jets, though in Syria, the military claimed Friday that one Israeli jet had been shot down and another damaged.

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One of the anti-air projectiles fired by the Syrian army was intercepted by Israel's "Arrow" missile defense system north of Jerusalem.

The Israeli army said the rockets fired toward Israel were not among Syria's most advanced and the incident was the first confirmed instance of operational use of the Arrow system - meant to challenge the threat of ballistic missiles - despite being first delivered to the army in the late 1990s.

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A Jordanian military source said that shrapnel had fallen within its borders as a result of Israel's interception of the Syrian missile.

According to the Israeli army, its aircraft had already returned to Israeli airspace when Syrian launched its air-defense rockets.

Prevailing assessments suggested that Israel was targeting shipments of weapons intended to reach Hezbollah in Lebanon. Hezbollah later denied reports that one of ts commanders had been killed in the airstrikes.

The Syrian army said that Israel had targeted a military site near Palmyra and swore to retaliate "directly, with all means at its disposal."

The statement from Syria accused Israeli jets of entering Syrian airspace from Lebanon and striking the country in support of ISIS.

There were no Israeli casualties in the incident, and the IDF military spokesperson's unit confirmed Israel struck targets in Syria in an exceptionally rare statement.

There have been several reports over the past five years that Israel has targeted weapons convoys in Syria headed for Hezbollah in Lebanon, but until now Israel has not officially addressed these claims.

The Assad regime's retaliation Thursday pointed to a decided shift in behavior toward Israel amid numerous reports on Israeli strikes.

Earlier in the night, the IDF confirmed sirens sounded in the Jordan Valley in eastern Israel.

Less than a month ago, on February 22, Lebanese reports indicated that Israeli forces had struck an arms convoy outside of Damascus in an attacked carried out from Lebanese airspace.

One month before that, on January 13, the Syrian government warned of repercussions to what it called a "flagrant" attack after the army told state media that Israeli missiles had struck a military airport west of Damascus.

Though always stopping short of confirming airstrikes in Syria until Thursday, Israeli officials have repeatedly sworn to take whatever action necessary to prevent weapons shipments to Hezbollah in Lebanon via Syrian territory.

In fall, 2016, the Israeli government reached an understanding of military cooperation with the Russian air force - also active in Syria - designed to prevent any accidental clashes.

Reuters contributed to this report.