this is bbc news. welcome if you're watching here in the uk or around the globe. our top stories: ukrainian president volodymyr zelensky has called for meaningful peace and security talks "without delay". he said it was russia's only chance to limit the damage from its "mistakes" following the invasion. fighting has reached the centre of the southern port city of mariupol. that's been confirmed by both sides. many civilians are still trapped in the city — and more than 80% of residential buildings are either damaged or destroyed. the white house says president biden has warned china there will be consequences if it supports russia in the war in ukraine. three russian cosmonauts have docked with the international space station. it's unclear whether their choice of yellow and blue flight suits colours, which resemble the ukrainian flag, was an intentional show of solidarity for ukraine.