Ukraine warned inhabitants of Russian-annexed Crimea on Monday to build bomb shelters and stock up on supplies as Kiev prepares for a strong counteroffensive to force Russian soldiers out of seized Ukrainian territory.

Ukraine has been warning citizens in its occupied south for weeks to prepare and flee before launching a counter-offensive. Nonetheless, Monday’s warning was remarkable since it was sent to inhabitants of Crimea, which Russia seized in 2014, rather than territories conquered by Russia during this year’s incursion.

The Black Sea peninsula is thought to be out of range of Ukrainian weapons, though several recent explosions at Russian military sites in Crimea have called that into question. Kyiv has declined to claim responsibility for the incidents.