Ukrainian forces are stepping up their counteroffensive in the country's east and south in an effort to retake Russian-controlled areas.

Ukrainian President Volodymyr Zelenskyy said on Thursday that since October 1, more than 500 square kilometers of territory and dozens of settlements have been liberated from Russian control in the Kherson region alone.

Britain's defense ministry said in its intelligence update on Friday that Ukraine has likely captured at least 440 Russian tanks and around 650 other armored vehicles since the invasion. It also said potentially over half of Ukraine's currently fielded tank fleet consists of captured vehicles.

Russian Foreign Minister Sergey Lavrov claimed in a video message on Friday that Zelenskyy has urged the leaders of Western nations to launch preventive nuclear strikes against Russia.

Lavrov added that the United States and its allies continue to provide Ukraine with weapons, and warned against further involvement by the US.

Russia's presidential office has announced that an informal summit meeting of the Commonwealth of Independent States, or CIS, will be held near St. Petersburg on Friday. The CIS is a Russian-led bloc of former Soviet republics.