Grant Shapps has said the Russian fleet in the Black Sea is "functionally inactive" following a set of strikes.
The defence secretary was speaking as Kyiv forces destroyed two large Russian warships, the Yamal and the Azov, in the Black Sea along with other navy facilities over the weekend.
Shapps said: "Putin’s continued illegal occupation of Ukraine is exacting a massive cost on Russia’s Black Sea fleet which is now functionally inactive.
"Russia has sailed the Black Sea since 1783 but is now forced to constrain [its] fleet to port. And even there, Putin’s ships are sinking."
Grant Shapps has said Putin's forces have been depleted in the area
Getty/PA
A spokesperson from the Ukrainian military said: "The defence forces of Ukraine successfully hit the Azov and Yamal large landing ships, a communications centre and also several infrastructure facilities of the Russian Black Sea Fleet in temporarily occupied Crimea."
A Moscow-installed official in the region reported a major Ukrainian air attack and said air defences had shot down more than 10 missiles over the Crimean port of Sevastopol.
Russian-installed governor of Sevastopol Mikhail Razvozhayev said that a 65-year-old man was killed when three homes were hit by shrapnel.
He added that transport infrastructure including passenger boats and buses were partially damaged, with windows broken on five boats. Three passenger buses, 13 school buses and one trolley bus were among vehicles damaged, he added.
LATEST FROM THE FRONTLINE IN UKRAINE:
Governor of Sevastopol Mikhail Razvozhayev
Reuters
It comes as Moscow has shifted its language relating to the conflict in Ukraine. For the past two years, people have been told to refer to the war in Ukraine as a "special military operation."
However, Kremlin spokesperson Dmitry Peskov told state media: "We are in a state of war. Yes, it started out as a special military operation, but as soon as this group was formed, when the collective West became a participant in this on the side of Ukraine, it became a war for us."
"I am convinced of that. And everyone should understand this, for their internal motivation."
The remarks appear to signal that Russia is digging in for an even longer standoff over Ukraine with the United States and its allies.
Kremlin spokesman Dmitry Peskov
Reuters
Author and expert in Russian affairs Mark Galeotti said: "That ‘internal mobilisation’ is actually the key thing: the Kremlin’s demand that every Russian get into a wartime mindset, and realise there is now no middle ground between being a patriot and a traitor (as Putin defines these)"
Peskov said that Russia must fully "liberate" its "new regions" to ensure people's safety there, a reference to the four Ukrainian regions which Russia claimed to have annexed in 2022 but does not fully control.
Russia, he added, could not allow a state to exist on its borders that had shown itself ready to use any method to seize control of Crimea.
Kyiv says Russia's annexation of the four regions is an illegal land grab and that it will not rest until every Russian soldier is ejected from its soil.