Wagner Group may be providing Pantsir anti-aircraft systems to the Lebanese militia Hezbollah, U.S. sources told the Wall Street Journal on Nov. 2.
According to one unnamed U.S. official, the transfer is still unconfirmed, and the situation is still being monitored.
The potential delivery is a "major concern," sources said.
Pantsir is a self-propelled air defense system with anti-aircraft missiles and guns to intercept planes and helicopters.
Iran-backed Hezbollah has thus far refrained from fully entering Israel's war with Hamas, although there have been crossborder clashes.
Nonetheless, Wagner Group providing an advanced air-defense system like the Pantsir would likely be considered a significant step and sign of Russia's troubled relations with Israel.
Although Israel has not been explicitly allied with Russia, it has largely neglected to actively oppose its war against Ukraine.
It has also refrained from providing any meaningful aid to Ukraine.
However, following Hamas' Oct. 7 attack on Israel, Russian officials have made increasingly sharp comments criticizing Israel and its wartime tactics, as well as greeting a Hamas delegation in Moscow on Oct. 25.
Israel's bombing campaign against Hamas in Gaza goes against international humanitarian law, Russian Foreign Minister Sergei Lavrov said on Oct. 28.
Russia's Permanent Representative to the United Nations, Vasily Nebenzya, spoke against Israel's "supposed right to self defense" at the UN on Nov. 2.
There has also been speculation that Russia may have been involved in Hamas' attack.
Tensions between Russia and Israel grew even further after antisemitic protesters stormed the airport in the Russian city of Makhachkala on Oct. 29, looking for Jews.
The fate of Wagner Group, Russia's most notorious mercenary group remained uncertain following its rebellion against the Kremlin in June and a plane crash that killed the group's leader and several other senior commanders two months later.
Russian media reported on Nov. 1 that the Wagner Group has allegedly resumed recruiting in the Russian cities of Perm and Novosibirsk as a unit of Rosgvardia, Russia's National Guard.