A barrage of Kalibr cruise missiles was launched from a diesel-electric submarine at Ukrainian military targets, the Russian Defence Ministry said.
News agency Interfax said it was the first such report after Russia described previous strikes on Ukraine as coming from frigates, aircraft and land-based missile systems.
However, Ukraine’s military had reported four days ago that missile strikes were coming from submarines, after analysts said there was evidence of Kilo-class subs loading up with weapons in the Black Sea.
Military spokesman Igor Konashenkov said sea-based Kalibr missiles had hit substations near the railway junctions Fastiv, Krasnosilka and Polonne, although he did not specify whether those were submarine strikes.
Ukraine has said that railway junctions were targeted to thwart the transport of military aid from European allies.
Kalibr missiles have been in service since the 1990s and are believed to have previously been used in submarine-launched strikes by Russian forces on Syria. Russia lost its Black Sea flagship Moskva in uncertain circumstances two weeks ago.
Mr Konashenko separately claimed Russian strikes on Kyiv on Thursday had been “high-precision, long-range” attacks that destroyed a rocket and space industry compound in the city.
But Radio Free Europe, a US-funded broadcaster, said one of the missiles hit a residential building and that one of its journalists, Vira Hyrych, had been found dead in the rubble.
And Ukrainian President Volodymyr Zelenskyy suggested the strikes had been timed to coincide with a visit to Kyiv by UN Secretary General Antonio Guterres, who toured sites of alleged Russian atrocities near the capital.
“This says a lot about Russia's true attitude to global institutions … about the efforts of the Russian leadership to humiliate the UN and everything that the organisation represents,” Mr Zelenskyy said.
Both sides claimed to have inflicted heavy losses on the other. Ukraine said Russia was continuing its assault in the eastern Donetsk and Luhansk regions as it tries to gain full control of the Donbas region.
Britain said in a regular intelligence update that what it called the “Battle of Donbas” was Russia’s main strategic focus but that territorial gains had been limited due to stiff Ukrainian resistance.
Russian President Vladimir Putin is widely believed to be seeking a military victory of some sort by the time of a symbolic military parade in Moscow on May 9, commemorating the former Soviet Union’s victory over Nazi Germany.
UK Defence Secretary Ben Wallace said this week that Mr Putin might use the opportunity to rally support by declaring Russia to be at war, dropping the terminology of a “special military operation” used by the Kremlin until now.