Ukraine's future hinges on the outcome of fighting with Russia in and around Bakhmut, President Volodymyr Zelenskyy said, with both sides describing relentless battles as Moscow intensifies a winter campaign to capture the small eastern city.

In what would be the first international war crimes cases arising from Russia's invasion, the International Criminal Court (ICC) is expected to seek the arrest of Russian officials for forcibly deporting children from Ukraine and targeting civilian infrastructure, a source told Reuters.

Moscow would be certain to reject arrest warrants against its officials. But an international war crimes prosecution could deepen Moscow's diplomatic isolation over a campaign that has killed thousands of civilians and drawn Europe's fiercest fighting since World War II.