London-based Patricia Daley, a 29-year-old barrister and Tokunbo Koiki, a 40-year-old social worker, spotted Korrine Sky's tweets on her journey trying to escape Ukraine.

The 26-year-old, who was studying in Dnipro, has now safely fled to Romania and documented her journey out of the country as Russian troops advanced.

The trio got in contact with each other on Twitter to coordinate the campaign after videos on social media appeared to show scenes in which black students were prevented from safely crossing the border.

The footage prompted hashtags including #AfricansinUkraine that began trending on social media amid concerns that black people trying to flee were facing racist treatment.

Around 660,000 refugees have now fled Ukraine to neighbouring countries in the past six days, according to the UN.

Ms Daley, Ms Koiki and Ms Sky told Sky News the money raised in the campaign had been used to help more than 500 black students escape Ukraine through funding transport costs, like arranging taxis and other emergency needs.

Ms Koiki said black students fleeing Ukraine who she had been in contact were terrified.

"People said they were pushed, sent back and physically assaulted on both sides of the border in Ukraine, Romania and Poland," she said.

Ms Daley said she had spoken to hundreds of black students in Ukraine, many of whom recounted racist abuse they faced while trying to flee.

She said students had sent her voice notes crying and in severe distress from their experiences, with some describing segregated gates for Ukrainians and non-white people.

"I do think they have been treated differently at borders because of their skin," Ms Daley said.

"Racism is now happening even in situations where there is war."

Morocco, Nigeria, and Egypt are among the 10 countries with the most students in Ukraine, between them sending more than 16,000 people to study in the country according to Ukraine’s education ministry.

Dr Ayoade Alakija, a WHO special envoy, described the scenes of racism shown in Ukraine and around its borders as "unacceptable".

The African Union has also raised concerns, with leaders in Senegal, Nigeria and a number of other African countries condemning the discrimination.