A convoy of 11 empty buses - driving towards Mariupol to rescue fleeing Ukrainians - has been commandeered by Russian forces, according to the Ukrainian government, writes CNN.

Russians have driven the buses, along with the original bus drivers and several emergency services workers, to an undisclosed location the government says.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said the buses were taken over at a Russian checkpoint outside Mangush, about 15 kilometers west of Mariupol.

Mariupol has been under devastating bombardment for several weeks and 100,000 people in the city are without water and access to medicines, President Volodymyr Zelensky said. A local Ukrainian officer in the city told CNN that bombs have been falling on the city every 10 minutes.