The ministry said Russia had destroyed two launchers for the High Mobility Artillery Rocket Systems (HIMARS) that the United States and its allies have been supplying to Kyiv.
It also said Russian forces destroyed two ammunition depots storing rockets for the HIMARS near the frontline in a village south of Kramatorsk in Ukraine's Donetsk region - the main focus for Russian troops following the capture of Luhansk over the weekend.
The ministry released video footage which it said showed the strike. Reuters could not independently verify the strike.
Ukraine had received only four HIMARS systems as of early July, the European Council on Foreign Relations said in a report. The US has pledged to deliver eight by mid-July.
Western weapon supplies have been crucial to Ukraine's efforts to push back the tens of thousands of Russian troops that Moscow sent into its pro-Western neighbour on Feb 24 in what it calls a "special military operation."