Updated at 4:15 p.m. on June 22 to clarify that a gas drilling platform, not an oil drilling platform, was struck.
Offiicals Russia-annexed Crimea has accused Ukraine of firing upon a gas drilling platform in the Black Sea Monday morning, with three injured and seven missing.
"This morning the enemy struck the drilling platforms of Chernomorneftegaz...I am in touch with colleagues from the Defense Ministry and the FSB," Aksyonov wrote in a post on the Telegram messaging app.
The drilling rig at Chernomorneftegaz's Odessa gas field was still on fire over 24 hours after the alleged strike, a Russian senator for Crimea said Tuesday.
"As for the fire, it is not subsiding on the platform. At night, the fire approached the oil well," Senator Olga Kovitidi told the Interfax news agency.
Kovitidi said that the "search continues" for the seven missing persons, while the three injured are in hospital but their condition is not critical.
Aksyonov, installed by Russia as the peninsula's governor after the 2014 annexation, had previously said five people were injured before revising the casualty figures.
Ukrainian officials have not yet commented on the alleged strike.
Mikhail Sheremet, a lawmaker in Russia's lower-house State Duma, said Moscow would respond with "retaliatory strikes" on Ukrainian "decision-making centers."
The Russian state-run RIA Novosti news agency cited a source as saying that the Ukrainian army attacked the drilling platforms near Tarkhankut, the southwestern cape of the peninsula.
Chernomorneftegaz is an oil and gas company that operates gas and oil fields in the Black Sea and the Sea of Azov.
The strike is the first reported Ukrainian attack against offshore energy infrastructure in Crimea since the start of Moscow's invasion in late February.
AFP contributed reporting.