Ukrainian President Volodymyr Zelenskyy has accused Russia of firing missiles from the Black Sea in its attack over the weekend, adding that Moscow is refusing to agree to a ceasefire.



The Ukrainian Air Force said the Russian military mounted an attack, launching 23 missiles and 109 unmanned aerial vehicles against many parts of Ukraine between Saturday night and Sunday morning. Authorities said the strike killed one person and wounded three others in the capital, Kyiv.



Zelenskyy said in a video address on Sunday that the attack included missiles fired from the Black Sea. He also said Russia wants to preserve its ability to strike Ukrainian cities and ports from the sea.



Zelenskyy stressed that Russian President Vladimir Putin does not want to end the war, and added that all forms of pressure on Russia must continue.



The US government said last month it reached agreements with Russia and Ukraine to ensure safe navigation and eliminate the use of force in the Black Sea. But Russia has claimed some sanctions have to be lifted as a condition for the agreement to take effect.



Meanwhile, the British Defence Ministry said in its analysis on Saturday that Russia's rate of advance has dropped month by month since last November.



It said Russia seized 143 square kilometers of Ukrainian territory in March -- about one-fifth the territory it captured in November. The ministry pointed out that Ukraine's counterattacks reversed some of Russia's gains around Pokrovsk, a key logistics hub in the eastern region of Donetsk.



The US Institute for the Study of War said on Sunday, "Ukrainian forces have conducted localized counterattacks in the Pokrovsk and Toretsk directions in recent weeks, regaining lost positions in these areas and contributing to slowing Russian advances in Ukraine."