U.S. warns of catastrophic consequences if Russia uses nuclear weapons in Ukraine

Ukrainian service members ride atop an armoured fighting vehicles, amid Russia's attack on Ukraine, in Kharkiv region, Ukraine September 24, 2022. REUTERS/Oleksandr Ratushniak

KYIV (Reuters) -The United States warned on Sunday of "catastrophic consequences" if Moscow uses nuclear weapons in Ukraine, after Russia's foreign minister said regions holding widely-criticised referendums would get full protection if annexed by Moscow.

Votes were staged for a third day in four eastern Ukrainian regions, aimed at annexing territory Russia has taken by force. The Russian parliament could move to formalise the annexation within days.