New Delhi, Mar 1 (IANS): As thousands flee crisis-hit Ukraine, Nigeria has condemned reports that its citizens, and those from other African countries, are being prevented from leaving the war-torn country, BBC reported.

Isaac, a Nigerian national living in Ukraine, who has been trying to gain entry into Poland, said that border staff told him they were "not tending to Africans".

On Sunday, Nigeria's Foreign Minister Geofrey Onyeama said he had spoken with his Ukrainian counterpart Dmytro Kuleba and had been assured that Ukrainian border guards had been given an order to allow all foreigners leaving Ukraine to pass without restrictions.

There have also been numerous reports of Ukrainian security officials preventing Africans from catching buses and trains going to the borders, BBC reported.

Nigeria's President Muhammadu Buhari said there are about 4,000 Nigerians in Ukraine, mostly students.

He said one group had repeatedly been refused entry to Poland so they travelled back into Ukraine to head for Hungary instead.

"All who flee a conflict situation have the same right to safe passage under the UN Convention, and the colour of their passport or their skin should make no difference," Buhari tweeted.