The attack took place on Wednesday and initially there was talk of around 30 fatalities.
"The Israeli enemy carried out an air attack, targeting a number of buildings in the city of Palmyra", Syria's defense department wrote at the time.
According to the Syrian Human Rights Observatory (SOHR), which monitors the conflict in Syria from the UK, many of the victims were said to be members of the al-Nujaba brigade, a Shia militia supported by Iran and where many, according to SOHR, are foreign nationals.
Israel has not commented on the reports, but the country usually does not do so regarding military operations in Syria.
Palmyra is located along an important road from Iraq through Syria. It was once the capital of the short-lived Palmyrene Empire, which stretched from present-day Turkey to Egypt. Nowadays, it is mostly known as an archaeological site.
Parts of the historical monuments were destroyed during the Syrian civil war. The ruins were listed on UNESCO's World Heritage List.
