The European Union will on Monday discuss tightening sanctions against Russia because of the invasion of Ukraine. Meanwhile, Ukrainian President Volodymyr Zelensky has sacked his top two law enforcement officials in a major shakeup.
Kyiv has accused Moscow of launching strikes against residential areas in eastern and southern Ukraine.
The attacks came after Moscow announced it would step up its military operations and Ukraine accused Russia of installing missile launchers at Europe's largest nuclear plant.
In Brussels, EU foreign ministers will meet to discuss additional sanctions against Moscow, which has already been hit with a series of punitive measures since the war started in February.
The bloc is considering banning gold purchases from Russia, and more Russian individuals may be placed on the EU blacklist.
"Moscow must continue to pay a high price for its aggression," European Commission President Ursula von der Leyen said after forwarding the proposed measures.
Brussels is expected to hold initial sanctions discussions Monday, but not make a same-day decision, according to a senior EU official.
Security sackings in Kyiv shakeup
In the Kyiv government's most serious shakeup since the invasion in February, Zelensky on Sunday announced that he was firing prosecutor general Iryna Venediktova and security chief Ivan Bakanov.
In a national address, Zelensky said over 650 cases of suspected treason and aiding and abetting Russia by Ukrainian security officials are currently being investigated, including 60 cases of officials whom he said have remained in territories occupied by Russia and are "working against our state.
"Such a great number of crimes against the foundations of national security, and the connections established between Ukrainian law enforcement officials and Russian special services, pose very serious questions to the relevant leaders," Zelensky said.
Three thousand missiles launched
Zelensky also highlighted the devastating military might Moscow has used against Ukraine, saying that Russian forces have launched more than 3,000 cruise missiles on targets in Ukraine.
The heaviest fighting continues to focus on the industrial east of Ukraine, and on Sunday, Donetsk regional governor Pavlo Kyrylenko accused Moscow of shelling "civilian infrastructure, especially education institutions".
Near Ukraine's Black Sea coast, the southern city of Mykolaiv came under "massive shelling" on Sunday, regional governor Vitaliy Kim said.
Kim added that several residential areas had been shelled in the region a day earlier, with three people killed in the village of Shevchenkove and one woman killed in Shyrokiv where a "residential building was destroyed".
'50,000 Russian troops killed or wounded'
In a BBC television interview broadcast Sunday, the head of Britain's armed forces, Admiral Tony Radakin, estimated that 50,000 Russian soldiers had been killed or wounded in the invasion, with nearly 1,700 Russian tanks and some 4,000 armoured fighting vehicles destroyed.
Radakin suggested that Russia's land forces may pose less of a threat now, but more than 20 weeks since the invasion began, Moscow said Saturday it would step up its military operations.
Defence Minister Sergei Shoigu "gave the necessary instructions to further increase" military pressure, according to his ministry.
The orders come after Ukraine's atomic energy agency accused Russians of installing missile launchers at the Zaporizhzhia nuclear plant and using the facility to shell the Dnipro region.
