A Mil Mi-8 helicopter of the Ukrainian Armed Forces crashed near the village of Sestriatyn in Rivne region's Radyvyliv district, killing four crewmembers and the commander, the press service of Ukraine's Ground Forces said on its Facebook page on Thursday.

"The preliminary information available indicates that four crewmembers and their commander from the 16th separate air force brigade of the Ground Forces of the Armed Forces of Ukraine (stationed in Brody, Lviv region) were killed in the air crash," it said.

Contact with the helicopter was lost at 23:27 Kyiv time on May 29, the press service said.

Rescue services and law enforcement agencies are working at the scene. A commission made up of representatives of the Defense Ministry, the General Staff and the Ground Forces command is heading to the site.

An investigation into the cause of the accident is underway.