Seventeen Kazakh servicemen were swept out to sea during a naval training exercise in the Mangistau region on September 24, regional authorities said. Twelve died, three were rescued and two remained missing as search operations continued.

The servicemen were taking part in a combat drill when conditions changed suddenly and winds strengthened, the regional government said in a statement. The incident occurred off Kazakhstan’s Caspian coast. Authorities had not released further details about the sequence of events.

President Kassym-Jomart Tokayev declared September 25 a day of national mourning. The search for the missing servicemen was continuing.