KYIV, Ukraine ( AFP) — A Russian strike on a military training site in northeastern Ukraine has killed six soldiers and wounded at least 10 others, the Ukrainian national guard said on Wednesday.

Ukraine’s Sumy border region — from where Kyiv’s troops launched last year’s major cross-border offensive into Russia’s Kursk region — has come under intensifying attacks in recent months after Moscow recaptured its territory.

“Six soldiers were killed and more than 10 wounded as a result of the attack, while they carried out exercises at a military shooting range,” Ukraine’s national guard said in a Facebook post, adding that an investigation has been opened into the incident.

Russia’s defense ministry had on Tuesday evening said it had launched a ballistic missile attack on the site.

“During reconnaissance activities ... a training camp” for Ukranian special forces was “detected,” it said in a social media post.

“Based on the received coordinates, an Iskander missile strike was launched.”

Russia also published footage showing the hit on what it said was a training camp in a wooded area.

Aerial footage showed one strike, sparking a large fire and sending a plume of thick black smoke billowing into the air.