Evacuated residents from the besieged city of Severodonetsk in Ukraine are suffering from chronic dehydration after weeks living underground, according to a doctor with Médecins Sans Frontières.

Dr Andrei Slavuckij, who is currently based near Kramatorsk, 100km east of Severodonetsk, told Prime Time that many evacuees are in a poor medical state.

Analysts believe that Russia is verging on an important symbolic victory in Severodonetsk, which is the administrative centre of Luhansk, one of two large Eastern provinces that make up the Donbas region.

Thousands have fled Donbas in recent weeks after Russian president Vladimir Putin pledged to "liberate" the region.

"Many of them were in quite chronic kind of dehydration – specifically some children and elderly as well," Dr Slavuckij said.

"There were lot of complications of their chronic conditions, because many of them – they were living without the continuous treatment they need. There were some bad wounds that were not treated properly since long time. So, physically and mentally, those people are completely exhausted."

Some of the last remaining residents, many of them elderly and vulnerable, are leaving under bombardment in dangerous conditions.

"Many of them are elderly people who do not want to leave. But, surprisingly, also some mothers and children are staying behind. They don't know where to go, they're scared," Dr Slavuckij said.

"It’s only after direct shelling starts permanently that some of them finally decide to leave. So it's quite dangerous then. People are hiding in underground mainly. Some of them, they live on the basement floor. And what they lack is simple water, clean water, and sometimes food."

In Severodonetsk, for example, from a former population of 120,000 people, less than 15,000 people remain.

Both sides say that Russian forces, and local pro-Russian separatists, now control between a third and half of the city.

With much of the infrastructure in the wider region destroyed, including internet and mobile phone networks, it’s also hard to get reliable information about access routes, as relief groups attempt to assist to the wounded, Dr Slavuckij said.