Israel’s military said one of its jets was shot down by antiaircraft missiles during strikes on Syrian targets after it intercepted an Iranian drone launched from Syria that had infiltrated its airspace, intensifying tensions between the two neighbors.

The F-16 aircraft crashed in Israeli territory, the military said Saturday, updating an earlier statement about how the plane was downed. The pilots ejected and one was taken to the hospital in a serious condition, it added.

Syrian state media called the strikes a “new Israeli aggression.” The shots set off warning sirens in northern Israel of an imminent rocket attack, the Israeli military said.

The U.S. blamed Iran for the clash and voiced concern about the escalation of violence, saying it “strongly supports Israel’s sovereign right to defend itself.”

“Iran’s calculated escalation of threat and its ambition to project its power and dominance, places all the people of the‎ region—from Yemen to Lebanon—at risk,” said State Department spokeswoman Heather Nauert. “The U.S. continues to push back on the totality of Iran’s malign activities in the region and calls for an end to Iranian behavior that threatens peace and stability.”


Iranian Foreign Ministry spokesman Bahram Ghasemi said earlier Saturday that Syria had a right to defend itself, according to the official Islamic Republic News Agency. The Israeli claim of the downing of an Iranian drone and Iran’s involvement in the downing of an Israeli jet were “too ridiculous to dignify a discussion,” he said.

While Israel and Syria have exchanged volleys frequently in recent months and the Israeli military has intercepted enemy drones, the incident Saturday was unusual in that Israel for the first time claimed it involved an Iranian unmanned aerial vehicle.

It was also the first time Israel has lost a jet during a strike in Syria, despite dozens of airstrikes in recent years.

The Israeli military “sees the Iranian attack and the Syrian response as a severe and irregular violation of Israeli sovereignty,” it said.


Hezbollah in a statement announced the beginning of a “new strategic phase” that will put an end to Israeli’s abuse of Syrian land and air. “We confirm that the developments of today absolutely mean the end of the old formula,” the party said in a statement released on Lebanon’s National News Agency.

Israel has amplified criticism of Iranian attempts to set up military bases and weapons factories in Syria in recent months, warning it would engage in a conflict with the Syrian regime should Iran and Tehran-backed Lebanese group Hezbollah entrench on its border.

The alleged involvement of Iran in Saturday’s incident heightens concerns that Israel could be drawn into a war with Syria and its allies.

“This direct Iranian operation against Israel is a major escalation,” said Dan Shapiro, former U.S. ambassador to Israel and national security adviser for the Obama administration.


“There is a risk of these events escalating into a full-blown conflict if Hezbollah is tempted, or instructed by Iran, to join the fray,” said Mr. Shapiro, who is now a senior fellow at the Tel Aviv-based Institute for National Security Studies.

A spokesperson for the Syrian regime couldn’t immediately be reached for comment on Saturday’s incident. An official at Iran’s United Nations mission didn’t immediately respond to a request for comment.

Iran has denied it is seeking to establish bases in Syria, but has said it would continue to defend Syrian territory from foreign forces.

Russia and Iran are the main backers of Syrian President Bashar al-Assad in the yearslong civil conflict in Syria and Tehran vows to destroy the Israeli state.


Israel fears that after the fall of Islamic State and as the Syrian regime consolidates power in large parts of Syria, Iran will set up military bases there that could threaten Israeli security.

Israeli Prime Minister Benjamin Netanyahu visited Moscow late last month for a meeting with Russian President Vladimir Putin to discuss Iranian attempts to further set up militarily in Syria and create precision missile factories on the ground there.

“I made it clear that we will not agree to either of these developments,” Mr. Netanyahu said in a statement after the meeting. “And will act accordingly.”

Israel has largely stayed out of the Syrian war, though it has launched some 100 airstrikes on what it has said were convoys ferrying Iranian weapons to Hezbollah through Syrian territory.

The military also has increasingly hit what it claims are Iranian-controlled military bases in Syria in recent months, increasing tensions between the two sides.

Later on Saturday, the Israeli military said it mounted a “large-scale attack” on 12 Syrian sites, including three aerial defense batteries and four Iranian targets that are part of Iran’s military establishment in Syria.

Those strikes come after the U.K.-based Syrian Observatory for Human Rights said Israeli missiles earlier this week had hit military targets near Damascus, the Syrian capital. The Syrian army said it had intercepted the strikes.

Israel also launched missiles in December against a military base controlled by Iran near Damascus, according to pro-regime media.

Warplanes in September also struck a Syrian facility north of the central city of Homs. Israel didn’t confirm that it had conducted the attack, but Israeli officials subsequently said the facility was producing arms for Iran and Hezbollah.

—Raja Abdulrahim, Asa Fitch and Felicia Schwartz contributed to this article.

Write to Rory Jones at rory.jones@wsj.com