Young cancer patients at Kyiv's largest children's hospital are being taken over the border into Poland as Vladimir Putin's forces continue to target the city.
Russia is bombarding major population centres in Ukraine, including in the capital Kyiv and the major cities of Kharkiv of Mariupol. It also claims to have taken the southern city of Kherson.
Patients at Kyiv's Ohmatdyt Children's Hospital were evacuated to other areas, including Poland, by bus on Wednesday as a miles-long armoured column of Russian forces approached.
The medical staff said they could not guarantee adequate health care and safety to 50 children with cancer due to the effects of the invasion.
Lesia Lysytsia, an onco-ophthalmologist, told The Washington Post on Tuesday. “We cannot stop their treatment. They’re at war with cancer every day.”
Sick children have been forced to shelter in the underground bunker at the hospital.
Dozens of children and their parents lay on mats, some needing additional oxygen and others connected to drips.
Older children who were too sick to go home or flee the capital with their families following Russia's invasion were also sheltering in the basement.
Ohmatdyt normally has up to 600 patients, but that number is now around 200, chief surgeon Volodymyr Zhovnir said on Monday.
He said: "These are patients who cannot receive medical treatment at home, they cannot survive without medication, without medical treatment and medical workers.”
Patients in intensive care who cannot be moved have been placed in relatively safe areas of the building.
The focus is also on the security of medical staff.
"We also must take care of personnel, because if they die or get injured, what do we do, who will treat patients?" asked Valery Bovkun, a microsurgeon at Ohmatdyt.
Zhovnir, the chief surgeon, said the hospital had stockpiled enough medications for a month but added that it needed food for newborn babies.
He said: "Of all things we need peace most ... all of this is the tip an iceberg ... people are, for example, asking me where to buy insulin for children, pharmacies are not open."
Meanwhile, Dr Michael Ryan, the executive director of the WHO Health Emergencies Programme, warned more than 2,000 people were currently on oxygen support for treatment for COVID-19 in Ukraine’s hospitals.
“We have children with childhood pneumonia, we have women with difficulties in labour,” he said.
The Russian invasion of Ukraine has killed more than 2,000 Ukrainian civilians and destroyed hundreds of structures, including transport facilities, hospitals, kindergartens and homes, Ukraine's emergency service said on Wednesday.
The UN’s refugee agency says that about 660,000 people have fled Ukraine for neighbouring countries since the Russian invasion.
Shabia Mantoo, a spokeswoman for the UN High Commissioner for Refugees, added: “At this rate, the situation looks set to become Europe’s largest refugee crisis this century.”