<span style="color: #222222;">Nigerian President Muhammadu Buhari has expressed displeasure at reported incidents of the mistreatment of some Nigerian nationals attempting to flee Ukraine.<br />''<br />'' A total of 4,000 Nigerian citizens are still stranded in Ukraine.<br />''<br />''In a statement on Twitter, the president's office said Ukrainian police and security personnel had reportedly refused to allow Nigerians to board buses and trains heading towards the Ukraine-Poland border.</span><br />