A Ukrainian disability campaigner could barely hold back the tears when she told of a young man with cerebral palsy who she said was killed in a Russian air strike near Kyiv.

Raisa Kravchenko, from VGO, a Ukrainian network of more than 100 local NGOs supporting people with intellectual disabilities, spoke to reporters in a virtual news conference on Thursday from her home in war-torn Ukraine.

She stayed behind to take care of her 37-year-old son who suffers from a behavioral disorder.

Like other disability campaigners, Kravchenko fears more of Ukraine's 2.7 million people suffering disabilities will die or be seriously wounded as the war continues and they struggle to evacuate.

Russia invaded Ukraine two weeks ago in what it calls a “special operation” to destroy its southern neighbor's military capabilities and capture what it regards as dangerous nationalists. It denies targeting civilians.

"The most vulnerable are persons with disabilities on wheelchairs, with visual impairments, hearing impairments... these are helpless people," Valery Sushkevych, the head of the National Assembly of Persons with Disabilities of Ukraine, told the conference.

The International Disability Alliance said there was little evacuation support for them, and even those who manage to get to refugee centers or shelters inside or out of the country face obstacles: from simple steps on stairs to inaccessible information.

"This is a humanitarian crisis within a crisis," said its head Yannis Vardakastanis. "The humanitarian response must make specific efforts to identify people in this situation."

The United Nations said on Friday that more than 2.5 million have already fled Ukraine and 2 million are internally displaced.

Sushkevych said attempting to flee for people with disabilities was daunting, with journeys of several days and huge crowds at train stations.

It is unclear how many have been able to flee. About 5,000 children from orphanages have arrived in Poland and it is likely that 10% of them are disabled, said Inclusion Europe.

From those unable to leave Ukraine, it is becoming harder to get medication, Kravchenko added.

The European Disability Forum said tens of thousands of people with disabilities lived in institutions which were "already cut off from their communities" and "risk being abandoned and forgotten."