The Greek government said it would deport 10,000 migrants to Turkey and move others inland to ease overcrowding at refugee camps on the Aegean islands.
The expedited measures come after a deadly blaze that destroyed housing containers and killed a mother and daughter at Moria refugee camp on the island of Lesbos.
About 12,000 people, more than four times the capacity at Moria, have been living there after an influx of migrants and refugees since July.
The plans to deal with Greece’s migrant crisis, unveiled after a special Cabinet meeting on Monday, mark the start of a more hard-line approach under the conservative government of Prime Minister Kyriakos Mitsotakis.
Athens will return 10,000 migrants who do not qualify for protection by the end of next year, to Turkey by the end of 2020, the government said.
It said it would increase the rate of returns from the "1,805 returned in the 4.5 years under the previous Syriza government".
The interior ministers of France and Germany are due to travel to Greece and Turkey this week with departing EU migration commissioner Dimitris Avramopoulos to address the crisis.
In 2016, the EU reached an agreement with Turkey aimed at discouraging refugees from entering EU.
Turkey agreed to take back migrants who entered Greece and send legal refugees to Europe.
German Chancellor Angela Merkel’s government has endorsed the move from Athens.
A spokesman said Berlin backed plans to increase the number of migrant deportations to Turkey.
Greek authorities have also said they will tighten their land and sea borders. The government in July announced more naval patrols in the Aegean.
To further ease the pressure on the island camps in Lesbos, Chios, Samos, Leros and Kos, each of which has at least double their capacity, Athens said it would move thousands of refugees to the mainland.
Under the plans, unveiled on Monday, the asylum seekers will be distributed nationally across all 13 regional authorities.
That brings to an end the policy of containment pursued by Greek authorities for the past three years after the migrant deal struck between Brussels and Ankara.
Christine Nikolaidou, a spokeswoman for the UN's International Organisation for Migration, told The National that the agency had prepared spaces for 5,000 asylum seekers on the mainland.
“The IOM is actively participating in co-ordination with the Greek authorities in all these island decongestion operations that are taking place,” Ms Nikolaidou said.
"We have 29 camps on the mainland and where it is feasible, in co-ordination with the Greek government we are trying to expand the capacity of the facilities.
"From June up to the middle of November we will have delivered about 5,000 new places for people coming from the islands."