The situation in Ukraine's southern Mykolaiv and Kherson regions is "increasingly hostile" following the loss of a Russian warship in the Black Sea, Ukrainian officials said on Saturday.
"During the past day, the situation in the south of Ukraine has been characterized by increasing hostile aggression," Ukraine's Operational Command South said in a video statement.
"Desperately trying to gain a foothold and hold on to the positions of the southern front, the world's most shameful army is pursuing civilians in Mykolayiv and Kherson regions," the statement added. "The work of snipers has been recorded in some areas."
Russian forces were "enraged by the losses in the Black Sea" -- an apparent reference to the sinking of the Russian guided-missile cruiser Moskva -- and had "intensified the missile threat" in the region, the statement continued.
Mykolaiv and several other settlements of the region have come under heavy fire, including from cluster munitions, the statement said.
The UN Human Rights Monitoring Mission in Ukraine has previously said it had received credible allegations that Russian armed forces have used cluster munitions in populated areas in Ukraine.
The nongovernmental organization Human Rights Watch (HRW) has also confirmed Russia's use of cluster munitions throughout the conflict.
Some background: The Moskva -- one of the Russian Navy's most important warships -- sunk in the Black Sea on Thursday.
Ukraine claims that it hit Moskva with missiles, causing it to sink. Russia has insisted the reason for the sinking was a fire. On Friday, the United States supported Ukraine's account, with a senior defense official saying that it believes that two Ukrainian Neptune missiles hit the Russian warship in the Black Sea.
Whether the ship lies at the bottom of the sea as the victim of Ukrainian missiles, Russian incompetence, bad luck or a combination of all three remains disputed.
On Friday, a spokesperson for the Ukrainian Armed Forces in southern Ukraine suggested that Russian missile attacks in the south since Thursday night were in retaliation for the Moskva's descent, telling a media briefing, "we all realize that we will not be forgiven."
"We realize that attacks on us will increase, that the enemy will try to take revenge," Humeniuk said. "We are ready, we are resisting."
CNN's Tim Lister, Olga Voitovych and Brad Lendon contributed reporting to this post.