Three soldiers were killed and 16 injured in a mishandled grenade explosion in Russia’s Belgorod region near the Ukrainian border on Sunday, Russian news agencies reported.

According to state news agencies, the explosion occurred in a cultural center repurposed for storage of ammunition by the Russian military. As of Sunday evening, eight more service personnel were reported missing, Interfax reported.

The TASS news agency said local officials attributed the careless handling of grenades as the cause of the explosion.

The 112 and Baza Telegram channels, linked to Russia’s law enforcement agencies, reported the dead and injured were conscripts mobilised to fight in Ukraine.

Belgorod is bordered by Ukraine’s northeast, where the city of Kharkiv has been targeted by numerous Russian missile attacks since last February’s invasion.

Explosions have also rocked fuel and ammunition stores, which Moscow said were Ukrainian attacks. Kyiv, without claiming responsibility, has described them as “karma” for Russia’s invasion.