The Syrian Observatory for Human Rights said Wednesday's attack targeted three sites in Palmyra, with one hitting an alleged meeting of pro-Iran groups that also involved commanders from Iraq's Al-Nujaba group and Lebanon's Hezbollah.

The toll has risen to "92 dead: 61 Syrian pro-Iran fighters", 11 of them working for Hezbollah, "and 27 foreign nationals mostly from Al-Nujaba, plus four from Hezbollah", the Observatory said.

The Britain-based war monitor, which relies on a network of sources inside Syria, had previously reported 82 dead, while the Syria defence ministry on Wednesday said 36 people were killed.

The UN deputy special envoy to Syria, Najat Rochdi, told the Security Council on Thursday that the raid was "likely the deadliest Israeli strike in Syria to date".

The Observatory said the strikes also targeted "a weapons depot near the industrial area" in Palmyra, a modern city adjacent to globally renowned Greco-Roman ruins.

Since civil war erupted in Syria in 2011, Israel has carried out hundreds of strikes in the country, mainly targeting the Syrian army and Iran-allied groups, but also killing many civilians.

The Israeli military has intensified its strikes on targets in Syria since it escalated its assault on Lebanon in late September.

*This story was edited by Ahram Online.