ZAGREB Oct 6 (Reuters) - Italy will begin relocating refugees this week under a European Union plan that aims to spread the burden of the continent's biggest migrant crisis since World War Two, the EU's migration commissioner Dimitris Avramopoulos said on Tuesday.

The EU plans to relocate a total of 160,000 migrants, mostly Syrians and Eritreans, from the frontline countries of Greece and Italy to other member states in the 28-nation bloc.

Speaking to reporters during a visit to the Croatian capital Zagreb, Avramopoulos said he would personally attend the departure of the first batch of migrants from Italy.

"I will leave to Italy for the very first relocation of Eritrean refugees to Sweden," he said. "I hope that next week we will also have the first relocation of Syrians from Greece to Luxembourg."

Italian Interior Minister Angelino Alfano will join Avramopoulos at Rome's Ciampino airport when the plane carrying about two dozen Eritreans leaves Italy on Friday morning, a government source told Reuters.

Avramopoulos is then scheduled to fly to the Italian island of Lampedusa to visit the island's "hotspot", a new immigration centre to be run jointly by EU and Italian officials to better identify migrants and refugees, the source said.

More than half a million people have poured into Europe this year fleeing war and poverty in the Middle East, Asia and Africa, prompting bitter disputes between member states about how to react and how to share out the responsibility.

Refugees and migrants arriving in Greece and Italy have been streaming north across the continent to reach more affluent nations such as Germany, triggering disputes between governments in central and eastern Europe as they alternately try to block the flow or shunt the burden on to their neighbours. (Reporting by Igor Ilic, additional reporting and writing by Steve Scherer in Rome; Editing by Gareth Jones)