The United Nations has warned of an imminent "mass exodus" of biblical proportions as catastrophic floods are set to hit parts of the world in the coming weeks. The UN's Office for the Coordination of Humanitarian Affairs (OCHA) has issued a warning to countries in Europe, Asia and Africa, saying that the floods could cause "dire consequences" for millions of people living in low-lying areas. The floods are expected to be caused by extreme weather events such as heavy rains, melting snow and ice, and rising sea levels. The UN estimates that over 500 million people are at risk of being affected by the floods. The UN is currently coordinating a global response to the crisis, and has urged countries to prepare for the impending floods by providing adequate shelter and food for those affected. The OCHA has also warned of the potential for displacement and mass migration, with hundreds of thousands of people potentially having to leave their homes in search of safety. The UN is calling on the international community to take urgent action to help those affected by the floods, and to provide assistance to those who are forced to flee their homes. The floods are expected to have a devastating impact on the global economy, with the UN warning of the potential for "catastrophic losses" in terms of infrastructure, livelihoods and lives. The UN has urged countries to work together to reduce the risk of flooding and to prepare for the potential consequences. The organization is also calling for increased investment in disaster risk reduction and climate change adaptation measures.