Germany and France led demands for Britain to negotiate a quick divorce from the European Union, with Paris warning that populism will otherwise take hold after the vote to leave the bloc sent shockwaves around the world.

Tens of thousands of people have taken part in a "day of action" in several European cities - and in Australia - in support of refugees and migrants.

German Chancellor Angela Merkel says the "breathtaking" flow of migrants into Germany will "occupy and change" the country in the coming years.