A Russian missile strike against a shooting range in Sumy Oblast on May 20 killed six service members and injured over 10, Ukraine's National Guard said.
"An official investigation into the tragedy is underway," the National Guard said in a statement.
The National Guard's command has established protocols and issued directives for responding to air strike threats and avoiding unnecessary concentration of personnel, the unit noted.
"The commander of the unit has been suspended, and the necessary information has been passed to law enforcement agencies," the statement read.
A Russian missile attack struck the Shostka community in Sumy Oblast in the afternoon on May 20, hitting an enterprise, the regional military administration reported at the time. The Air Force also issued warnings about Russian aerial attacks in Ukraine's northeastern regions.
The Russian state news agency TASS claimed that a Ukrainian military training ground was hit by an Iskander missile.
Both Ukraine and Russia rarely acknowledge successful attacks by the opposing side against their military facilities and encampments.