The death toll from a series of Israeli strikes in the Syrian city of Palmyra has climbed to 71, mostly Iran-backed fighters, a monitor reported Thursday.

The U.K.-based Syrian Observatory for Human Rights said those killed in Wednesday's strikes included 45 fighters from pro-Iran Syrian groups, 26 foreign fighters, most of them from the Iraqi al-Nujaba movement and four from Lebanon's Hezbollah.

The strikes targeted three sites in the city renowned for its ancient ruins, including one that hit a meeting of pro-Iranian groups with leaders from al-Nujaba and Hezbollah.

The Observatory, which relies on a network of sources on the ground across Syria, had previously put the toll from the Israeli strikes on Palmyra at 61 dead.

Syria said the Israeli strikes on the central city killed 36 people and wounded more than 50 others, in the latest toll issued by the Defense Ministry.

"The Israeli enemy launched an air attack from the direction of the al-Tanf area, targeting a number of buildings in the city of Palmyra," it said Wednesday.

The strikes targeting Palmyra – a modern city adjacent to Greco-Roman ruins – are the deadliest in Syria since a year of cross-border clashes between Israel and Hezbollah intensified in late September.

In a separate statement, the Syrian Foreign Ministry condemned "in the strongest terms the brutal Israeli aggression against the city of Palmyra, which reflects the continuing crimes of Zionism against the countries of the region and their peoples."

Israel rarely comments on individual strikes in Syria but has repeatedly said it will not allow Iran to expand its presence in the country.

Palmyra, a UNESCO World Heritage Site, was taken over and pillaged by Daesh terrorists at the height of the Syrian civil war.

The director general of Antiquities and Museums in Syria, Nazir Awad, told AFP the city's temples "did not suffer any direct damage" during the latest strikes.

"We need to conduct a survey on the ground to confirm these observations," he added.