The Syrian ministry notes that the Israeli warplanes attacked from the border triangle area in Tanaf. (NEWSRAEL: There is a US base in this area) 

Syrian opposition sources confirm that the flight path of the Israeli planes for the purpose of the attack was as marked on the attached map with blue arrows.

This is an unusual amount of casualties, especially in an attack in Syria.    

Here is the earlier report from the independent Syrian Observatory for Human Rights (SOHR):

Homs province: Israeli fighter jets executed several airstrikes on three positions in Palmyra city: a weapons warehouse near the industrial area which is inhabited by families of Iranian-backed fighters of Iraqi and other non-Syrian nationalities in Al-Jam’iyah neighbourhoods, another position in the same neighbourhood and a nearby position.

It is worth noting that those families have been resettled in the houses which had been seized by Iranian-backed militias in Palmyra city. In addition, those families have seized shops, rest houses and restaurants in the archaeological city for their own benefit.

According to SOHR sources, the Israeli strikes resulted in the death of at least four Iranian-backed non-Syrian militiamen and seven other Syrian militiamen, as well as the injury of tens others, including at least seven civilians who sustained serious injuries.

It is worth noting that Israeli fighter jets had flown over Daraa countryside and Al-Tanf area, before attacking those positions in Palmyra city.