``Behind the backs of our guys in Mariupol there are around a thousand civilians, including women and children,'' he said after talks with European Council President Charles Michel.

Zelenskyy added that Russia has stonewalled Ukraine's attempts to negotiate a safe exit for them. ``We are open to different formats of exchange of our people for Russian people, Russian military that they have left behind,`` he said.

Ukraine also has tried to get Russia to agree on a humanitarian corridor to evacuate the 120,000 people who Zelenskyy said to remain under siege in Mariupol.