About 660,000 people have fled from Ukraine to neighboring countries, the UN Refugee Agency said, AP reports.

UN High Commissioner for Refugees spokeswoman Shabia Mantoo said that at this rate, the situation looks set to become the biggest refugee crisis in Europe this century.

She said the agency urges governments to continue allowing access to all those who flee, including third-country nationals living in Ukraine who are forced to flee the violence

We stress that there must be no discrimination against any person or group, she added.