Title is misleading, you should ignore the '500' of the title as the statement is cut short of it's context. Russian MoD is claiming over 500 Ukrainian soldiers killed for the entire Donetsk front and not from the strike itself, and claims are made from body counts where there is force to force contact. While the strikes may incur an unknown number of casualties, they're not part of the '500' tally for the entire Donetsk front, including Bakhmut, Avdiivka all the way to Ugledar. As for the strike itself this appears to done with MLRS, and I'm guessing the culprit being Tornado-G, which is the modernized Grad with Glonass guidance.
Even as the Ukrainians are doing probing attacks all across all fronts, the Russians are methodically targeting brigade level headquarters, ammo and fuel depots, barracks, command and observation posts all across the fronts, with aerial bombs, drones and guided MLRS.
This appears to be a Nona, one of the most underreported but well used weapons of the war in both sides. The idea is an SPG around a 120mm mortar. The idea is that these things can shoot and scoot.