Russia's defense ministry has reiterated its demand that defenders of the southeastern Ukrainian city of Mariupol surrender.

The ministry issued an emergency statement on Tuesday calling for Ukrainian forces to lay down all arms and ammunition. It also demanded that they leave the steel plant where they'd been holed up between 2 p.m. and 4 p.m. local time to surrender.

The ministry had issued a similar demand on Sunday, but the Ukrainians refused and vowed to fight to the end.

The statement warned of an unbearable fate for those who continue to resist, suggesting the Russians are set to launch a fierce offensive even though Ukraine says more than 1,000 civilians are sheltered at the plant.