Syria says Israeli strikes killed 16 amid widening tensions

Iran-backed Syria, led by President Bashar al-Assad, said Monday that the strikes late Sunday hit several areas across the country, wounding 36 people and damaging residential buildings. The missiles also targeted military sites in the eastern Syrian city of Masyaf, the country’s state news agency reported, adding that air defenses downed some of the projectiles.

Israel has accused Iran of using a scientific research center in Masyaf to develop weapons and missiles intended for its aligned regional militias, including Hezbollah, said Joe Truzman, a research analyst at the Washington-based think tank, Foundation for Defense of Democracies.

“Despite the ongoing conflict on multiple fronts, Israel remains steadfast in its campaign against suspected Iranian arms transfers," he said.

Iran’s Foreign Ministry condemned the strikes in Syria on Monday on state-run news agency IRNA, but denied it had any military sites in the country.

Israel has expanded an air campaign against enemy targets in Syria since the start of the war against Hamas in Gaza, blowing up weapons and fuel supplies destined for Hezbollah, which has backed its Palestinian ally by firing rockets on Israeli towns and cities.

To limit the fallout, Israel has avoided publicly claiming responsibility for attacks in Syria. Israel’s military didn’t respond to a request for comment Monday on the latest strikes.

The Israeli campaign of airstrikes in Syria began about a decade ago, as the civil war in the Arab country left a security vacuum that was filled by Iran and its allied militias, which backed Assad.

Israel so far has avoided dragging Syria into its fight against Hamas and Hezbollah. But it has had to walk a fine line between conducting attacks that kill militants and destroy arms supplies, while avoiding strikes that kill senior officials or large numbers of civilians and risk sparking a bigger blowup.

A strike in April on a gathering of Iranian military leaders in the Syrian capital Damascus provoked a rare direct attack on Israel from Iran and sparked fears for weeks that the two sides would engage in broader conflict, before tensions eased.

Since the start of the war in Gaza in October, more than 180 strikes in Syria have been attributed to Israel, an uptick compared with recent years, according to Armed Conflict Location & Event Data, a nonprofit, and Tel Aviv-based think tank the Institute for National Security Studies.

The Syrian leader has refrained from joining Iran-backed allies in launching attacks on Israel during the Gaza war, as he continues to fight a civil war against Kurdish and Islamic state forces.

The drumbeat of attacks hasn’t stunted Hezbollah’s military buildup. Some former Israeli officials have called on the military to expand its campaign as Israel also looks to more proactively engage the Lebanese militia in Lebanon.

Israel and Hezbollah have so far managed to avoid an all-out conflict even as they have exchanged near-daily fire over the past 11 months of war in Gaza, destroying towns and driving out tens of thousands of civilians on both sides of the border.

A growing number of Israelis have called for the military to act more aggressively to eliminate the threat from Hezbollah and return people to their homes.

On Monday, the Israeli military said it had mounted a series of airstrikes overnight against Hezbollah in response to rocket attacks and later said two hostile aircraft had entered Israeli airspace from Lebanon. The incidents appeared to be in keeping with the current rules of engagement between the two sides.

Saleh al-Batati and Adam Chamseddine contributed to this article.

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