Intended to flex Russian military muscle along the border with NATO countries to the west of Russia, the exercises have also highlighted some safety lapses. Already one Russian soldier has died from a ricocheting tank shell.

The Russian military issued a strongly worded statement denying that the helicopter mishap occurred on Monday, when President Vladimir V. Putin visited the firing range. But it did not dispute the authenticity of the video.

“The targeting system on one helicopter mistakenly acquired a target,” the statement explained. “The strike by unguided rockets damaged a truck.”

“All reports on social media of salvos fired at a crowd of journalists and a large quantity of gravely injured people are intentional provocations, or somebody’s personal stupidity,” the statement said. It did not clarify whether anyone was wounded in the misfire.

The news portal said an unidentified witness had provided the video, and suggested the mishap at the Luzhsky firing range occurred either Sunday or Monday. A longer video posted by another news site, Fontanka, shows civilian cars and a military truck damaged by shrapnel.