The so-called Syrian Observatory for Human Rights (SOHR) said the attack took place in the early hours of Monday, when unnamed aircraft opened fire on alleged gatherings of Lebanese and Iraqi fighters in the Syrian city of Boukamal, east of Dayr al-Zawr province, Presstv Reported,
Syrian sources, including the state-run al-Ikhbariyah Syria television, confirmed that the attack had indeed targeted Iraqi and Lebanese forces.
Hours later, the Israeli military took responsibility, claiming that it had carried out the drone attack against forces allegedly attempting to fire rockets into Israel overnight.
The London-based SOHR, which is linked to foreign-backed militants in Syria, claimed that at least 18 people were killed in the attack.
The drone strike comes amid the Israeli regime's renewed campaign of aggression against several countries in the region -- including Syria, Iraq and Lebanon.
The regime on August 24 targeted Hezbollah structures in the Syrian capital of Damascus, killing two members of the Lebanese movement. It also attempted to attack Beirut the next day but lost two drones over the Lebanese capital.
Hezbollah vowed swift retaliation back then, a promise that it took only days to fulfill.
On September 1, Hezbollah fighters targeted an Israeli military vehicle and several military bases along Lebanon's border with the occupied territories.
Hezbollah also announced early Monday that it had shot down another intruding Israeli drone.
Israel has on several occasions also targeted Iraqi Popular Mobilization Units (PMU), or Hashd al-Sha'abi.
The PMU, after purging Iraqi lands from Daesh and other foreign-backed militants, has been working with Syria to secure border areas between the two countries.
The attack on Monday came amid reports that Syrian and Iraqi officials are working to reopen a key border crossing that connects Boukamal to Iraq's al-Qaim as they continue to forge greater relations.
On Sunday, Iraq called for the return of Syria to the Arab League as the group opened its 152nd session in Cairo, Egypt.
The Arab League froze Syria's seat in 2011, at the onset of what would become a years-long war against foreign-backed militancy.
However, more Arab countries have called for normalization of ties with Syria and the government of President Bashar al-Assad, who has been able to push militants out of most of his country thanks to help from Russia, Iran and Hezbollah.