The four long-delayed "hotspot" centres will open on the islands of Lesbos Chios Leros and Samos which have been struggling to cope with a relentless flow of migrants landing from Turkey.

A fifth centre on the island of Kos will be ready "in five days" despite strong opposition from the local mayor and residents over the impact on the tourism industry Kammenos told reporters in Athens.

On Sunday riot police fired tear gas at protesters on Kos angry at plans to open a centre on the resort island.

More than 850000 migrants fleeing war and poverty in the Middle East and elsewhere transited through Greece last year on their way to northern Europe.

Greece has faced heavy pressure from fellow members of the European Union to control its borders better with the bloc giving Athens a three-month ultimatum last week to remedy "deficiencies" or effectively face suspension from the Schengen passport-free zone.

A government source had said Monday that the centres would open in time for an EU summit at the end of the week.

Each of the "hotspot" facilities will have enough prefab housing to accommodate 1000 migrants who will spend three days being registered having their fingerprints taken and being sorted between those eligible for asylum in the EU and economic migrants facing eventual deportation.

One aim will be to help spot jihadists using the migrant crisis to enter Europe -- a pressing concern after two of the men who carried out November's attacks in Paris sneaked in via Greece posing as refugees.

The hotspot centres were supposed to open late last year but have faced repeated delays.