"Unfortunately, the humanitarian situation in Ukraine is continuing to deteriorate rapidly, and in some cities it has reached catastrophic proportions," said the head of the Russian National Defence Control Centre, Mikhail Mizintsev.

He accused Ukrainian "nationalists" of laying mines in residential areas and destroying key infrastructure including roads and bridges leaving civilians with no access to electricity, water, food and medicine.

Mizintsev said that an especially dire humanitarian situation was developing in the southeastern port city of Mariupol, accusing Ukraine's "nationalists" of trapping hundreds of thousands of people in the besieged city.

"Hundreds of thousands of people, including foreigners, are being forcibly held by nationalists," he said.

He also accused Ukraine's military of holding hostage nearly 7,000 people from 16 foreign countries and crews from more than 50 foreign vessels.