“Hitting such an object always has a very powerful result, not only in terms of firepower, but also in terms of moral and psychological impact,” Natalia Humeniuk, the spokeswoman for the Ukrainian military southern command, said on Ukrainian television. “Because hitting command and control points always adds more confusion to the command and control of troops.”

The intensified attacks on Sevastopol and Russia’s military fleet come as Kyiv is trying to secure part of the Black Sea following Moscow’s withdrawal from a deal that allowed Ukraine to export its grain by sea. Russia’s military warned at around the same time that it would consider any ship approaching a Ukrainian port a potential military threat.

Iulia-Sabina Joja, the head of the Black Sea Program at the Middle East Institute research group, said Ukrainian forces have since targeted the Black Sea Fleet in part to force it to stay away from a safe corridor that Kyiv has been trying to establish for civilian freighters in the northwestern part of the sea.

This week, two ships loaded with grain safely sailed through the corridor, and on Saturday the American ambassador in Kyiv said three more cargo ships were expected to use the same route.

Here’s what else is happening in the war:

• Russian Attacks: Russian forces attacked multiple cities and villages over the past day, Ukrainian authorities said on Saturday. At least three civilians were killed and dozens of others injured in strikes on the Kherson, Zaporizhzhia and Poltava regions.

• Poland Dispute: President Andrzej Duda of Poland said on Friday that a dispute with Ukraine over grain imports would not significantly affect the countries’ bilateral relations, in an apparent move to ease recent tensions. Poland last week decided to maintain a ban on Ukrainian grain imports, in defiance of the European Union’s policy, arguing that cheap Ukrainian grain undermined its domestic market.

  The move prompted Ukraine to filed a complaint before the World Trade Organization, and President Volodymyr Zelensky to tell the U.N. General Assembly that some European countries were politicizing the grain issue. Poland is holding general elections next month in which farmers form an important voting bloc.

• Zelensky Trip: Mr. Zelensky has wrapped up his trip to North America, writing Saturday on social media that he held an unscheduled meeting at the airport in Shannon, Ireland, with the leader of Sudan’s military, Gen. Abdel Fattah al-Burhan. Mr. Zelensky had been in Canada on Friday following his appearance at the General Assembly and visit to Washington.