BRUSSELS (AFP) - The European Union has announced an emergency summit in Brussels next Wednesday to tackle the migrant crisis and address sharp differences over plans to relocate 120,000 refugees around the bloc.

"I convene an extra EUCO (summit) on Wednesday 23 September at 18h (12am Singapore) to discuss how to deal with the refugee crisis," Tusk said in a tweet.

German Chancellor Angela Merkel and her Austrian counterpart Werner Faymann had called for a summit after EU interior ministers in Brussels failed to reach a agreement Monday on how to redistribute refugees from overstretched Hungary, Italy and Greece.

Interior ministers from the 28 member states are to hold a new emergency meeting next Tuesday on Europe's worst migration crisis since World War II.

Tusk had last week warned that he would call a special summit if the ministers failed to agree on a solution at the Brussels meeting, warning of the need for "solidarity and unity." Pressure for action mounted on Thursday after the European Parliament backed the relocation plan for the 120,000 refugees.