Syria's health minister said Monday that overnight Israeli strikes killed 18 people in central Hama province, updating earlier figures, while a war monitor gave a higher death toll for the raids on military sites.
The Israeli military, which has carried out hundreds of strikes in Syria since its civil war started in 2011, declined to comment on the latest reported attack.
"The number of martyrs of the brutal Israeli aggression reached 18 martyrs and 37 wounded," Syria's Health Minister Hassan al-Ghabash told AFP.
This was "one of the most violent Israeli attacks" in Syria in years, the head of the Syrian Observatory for Human Rights war monitor, Rami Abdel Rahman, told AFP.
Earlier, official news agency SANA, citing a medical source, said the number of dead "in the Israeli aggression on a number of sites on the outskirts of Masyaf" was "16 martyrs and 36 wounded, including six critically".
SANA citing a military source reported that at "around 11:20 pm (2020 GMT) on Sunday, the Israeli enemy carried out an air attack" from the direction of northwest Lebanon "targeting a number of military sites in the central region".
Air defences "shot down some" of the missiles, SANA reported.
The Observatory war monitor reported "intense Israeli strikes" overnight, providing an updated toll of 26 dead including "five civilians, four soldiers and intelligence personnel and 14 Syrians working with pro-Iran groups".
Three more bodies were unidentified, it added.
Israeli strikes on Syria since 2011 have mainly targeted army positions and Iran-backed fighters including from Lebanon's Hezbollah group.
Israeli authorities rarely comment on individual strikes in Syria, but have repeatedly said they will not allow arch-enemy Iran to expand its presence in the country.
The Britain-based Observatory, which relies on a network of sources inside Syria, had earlier said the strikes targeted sites "where pro-Iran groups and weapons development experts are stationed".
The Observatory said "Israeli strikes... targeted the scientific research area in Masyaf" in Hama province and other sites, destroying "buildings and military centres".
Observatory chief Rahman said Iranian experts "developing arms including precision missiles and drones" worked in the scientific research centre that was hit.
Charred cars were visible on both sides of the road, with nearby trees still burning, observed an AFP correspondent present at the scene as part of a media tour organised by authorities.
The raids also blew five large craters in the main road to Masyaf, the correspondent said.
Iranian foreign ministry spokesman Nasser Kanani told a media briefing: "We strongly condemn this criminal attack by the Zionist regime on Syrian soil."
Syria's foreign ministry condemned the raids, accusing Israel of trying to "provoke a further escalation in the region".
Israeli raids on Syria surged after Hamas's October 7 attack on Israel sparked war in Gaza, then eased somewhat after an April 1 strike blamed on Israel hit the Iranian consular building in Damascus.
Syria has sought to stay out of the Israel-Hamas conflict, whose fallout has raised fears of a broader regional war.
In late August, several pro-Iranian fighters were killed in Syria's central Homs region in strikes attributed to Israel, the Observatory had said.
Days later, the Israeli military said it killed an unspecified number of fighters belonging to the Hamas ally Islamic Jihad in a strike in Syria near the Lebanese border.
The Syrian government's brutal suppression of a 2011 uprising triggered the conflict that has killed more than half a million people and drawn in foreign armies and jihadists.
Iran-backed groups including Lebanon's powerful Hezbollah movement have bolstered President Bashar al-Assad's forces during Syria's civil war.
Israeli raids on Syria have also sought to cut off Hezbollah supply routes to Lebanon.
