The Schengen Area consists of 26 European states which abolished any type of border control between their mutual borders. Countries included in the Schengen Area have a common visa policy for citizens of other states.
The Schengen agreement and the current migrant-sharing mechanism are deeply flawed and need urgent fixing, French President Emmanuel Macron has said. Europe must "have borders" even if it means a smaller Schengen zone, he said.
Right-wing and populist figures have called for an end to free movement in Europe in the wake of the Berlin truck attack, after the chief suspect was found to have fled through France all the way to Italy.
The German government wants to extend border control in the Schengen zone because it has had a tip-off about potential terrorists entering the country disguised as refugees, Germany's Der Spiegel magazine said.