Ukraine has launched missiles against three gas rigs in the Black Sea, according to Russian officials, south of Odessa.
Authorities in Ukraine said the Kremlin was using the trio of production platforms to host air defence and radar units, according to newspaper reports.
In the wake of the attacks on Monday, Sergey Aksyonov, head of occupied Crimea, said reported that seven people were missing and three others were injured following the attacks.
He added that a rescue operation is underway with patrol ships and aviation.
The Black Sea rigs, known as the Boyko towers, were seized by Russia from Ukraine back in 2014 to boost Russian control of air and sea in the area.
Formerly operated by Ukraine’s Chernomorneftegaz, the vessels were seized by Russia when it annexed the Crimea Peninsula.
Footage reportedly taken from a Russian rescue vessel in the area has shown one of the rigs leaning to one side with firefighters seeking to control the blaze on board.
Russian state media said 100 people were on board the vessels at the time of the attack.