Kyiv is working with allies on security guarantees akin to NATO's mutual protection pledge, Ukraine's president Volodymr Zelensky has said. Officials from Ukraine and allies the U.S., the U.K., France and Germany met in London on Thursday in a week when a peace proposal was produced which outlined an Article 5-like agreement which would be backed by Washington.

The president’s comments came after he said Crimea “will stay with Russia,” a position backed by the mayor of Kyiv, who conceded that his country may have to give up territory.

The Kremlin said it reserves the right to use nuclear weapons if it faces aggression by Western countries. Overnight, Moscow attacked Kyiv, killing at least eight people.