Internally displaced people (IDPs) are among the most neglected citizens, a United Nations-mandated body says.
The Russian Federation has at least 360,000 displaced people
In a report, the Global IDP Project said Europe alone had three million among 25m worldwide, far more than those enjoying refugees status.
The report calls on governments to take more care of IDPs by granting them the same rights as they would have at home.
In addition, it urges the international community to address the causes of forced displacement.
Dennis McNamara, director of the UN's interagency campaign to help the displaced, said displaced people remained "the least well-responded to of all humanitarian crises".
The Global IDP Project, a non-governmental organisation based in Geneva, looked specifically at displaced people in member states belonging to the Organisation for Security and Co-operation in Europe (OSCE).
Thousands, its report said, abandon their homes after war or civil strife but do not cross international borders.
Many IDPs are trapped in extremely difficult living conditions, with little or no access to housing, education, jobs or health care, the report says.
The BBC's Imogen Foulkes in Geneva says internally displaced people do not enjoy the protection of a UN convention as refugees do.