Ukraine's Main Military Prosecutor Anatolii Matios wrote on Facebook, Censor.NET reports.
"According to preliminary findings of the investigation carried out by the military prosecutor of the Kharkiv garrison (who is now at the scene), a subversive action triggered the explosion at several missile and tube artillery ammunition dumps (with 125 and 152 mm tank and artillery shells in stock) near the city of Balakliia in the Kharkiv region tonight at 2:56 a.m. A fire consequently broke out and caused further detonation of ammunition," he wrote.
Matios also said the perimeter of the danger zone has been secured. No casualty report is currently available. The region's authorities and law enforcement officials left for the scene.
A special commission led by Deputy Defense Minister for Combat Materiel Ihor Pavlovskyi left for the scene from Kyiv at the instruction of the Minister of Defense.
Local residents are being evacuated over the possible expansion of the danger area.
"We take all possible measures to prevent casualties, establish witnesses of the subversive action and examine the scene. The State Border Guard Service tightened the border control in the southeastern direction," Matios added.
Related materials: Explosions at Balakliia ammunition depot