Dmytro Gurin, a member of the Ukrainian parliament who is from Mariupol, tells me he believes Russia is trying to starve the city to force its surrender.

Ukraine has rejected a Russian deadline for its forces to stop fighting in the besieged port city, saying there could be no question of soldiers laying down their arms. Gurin has said the city, where an estimated 300,000 people are trapped, will not surrender.

"Russians don't open humanitarian corridors, they don't let humanitarian convoys enter the city," he says.

"We clearly see now that the goal of the Russians is to start to [create] hunger [in the city] to enforce their position in the diplomatic process, and if the city does not surrender, and the city will not surrender, they won't let people out."

Gurin says teams are still unable to clean through the rubble of a theatre which Ukrainian officials say was bombed by Russia last Wednesday. Hundreds of people are believed to remain trapped in the basement, which withstood the attack. Moscow denies targeting the building.

"The services cannot clean this rubble because the shelling never stops and bombing never stops. It’s really dangerous," he says.

Gurin could not give an estimate on how many people had managed to flee the area as "we don't have connection with Mariupol".