Official: Russian forces kidnapped mayor of occupied Kherson.

"We must be prepared for the scale of war our grandparents and great-grandparents endured," NATO Secretary General Mark Rutte warned.

Russia’s Slavneft-YANOS oil refinery in Yaroslavl, one of the country’s five largest, is reportedly on fire after being struck in an overnight drone attack on Dec. 12, officials and local Telegram channels said.

U.S. President Donald Trump is "extremely frustrated" with both Russia and Ukraine amid ongoing diplomatic efforts to end the war, White House press secretary Karoline Leavitt said during a Dec. 11 press briefing, as the United States weighs whether to join Ukraine and European partners for talks this weekend.

A Russian airstrike on Odesa on Dec. 12 damaged infrastructure and left parts of the city without electricity and water, the head of the Odesa Military Administration, Serhiy Lysak, reported.

A drone explosion damaged the lower floors of a residential building in the Russian city of Tver on Dec. 12, injuring at least seven people, according to regional officials and local Telegram channels.

Polish authorities have detained Alexander Butyagin, a Russian archaeologist accused of causing extensive damage to historical sites in occupied Crimea, at the request of Ukraine's prosecutor general, Polish media reported Dec. 11.

The Kyiv City Prosecutor's Office said it has classified two explosions that killed one person and injured four others in Kyiv on Dec. 11 as a terrorist attack, the office said in a statement.

The European Commission and Kyiv have agreed on a 10-point action plan to tackle corruption and strengthen democratic institutions in Ukraine as part of its path to membership, EU Enlargement Commissioner Marta Kos announced.

"The Russians want the whole of Donbas — we don't accept that," President Volodymyr Zelensky said. "I believe that the Ukrainian people will answer this question," he added.