More than a dozen boats carrying migrants arrived in Greece on Thursday.
Athens has announced stricter border patrols, alongside plans to move asylum-seekers from its islands to the mainland and speed up deportations in an effort to deal with a fresh migrant influx from Turkey.
Greece's Council for Foreign Affairs and Defence met on Saturday for an emergency session after more than a dozen boats carrying around 600 people landed off the coast of the Greek island of Lesvos on Thursday.
It is the largest arrival of migrants — mostly Afghan families — in a single day on Lesvos since 2016.
On Saturday the Greek government said the measures include stepping up border controls with the European Union's border patrol agency Frontex and NATO, moving asylum seekers to the mainland, and identify rejected asylum seekers who may have remained in the country.
It also wants to shorten the country's lengthy asylum process, which can take several months, and make it easier to deport applicants to Turkey or their country of origin.
"The asylum process in our country was the longest, the most time consuming and, in the end, the most ineffective in Europe," Greece's deputy citizen protection minister responsible for migration policy, Giorgos Koumoutsakos, told state television.
Responding to critics from the opposition that the move was unfair and unlawful, he said: "Asylum must move quickly so that those who are entitled to international protection are vindicated... and for us to know who should not stay in Greece."
The government was "determined to push ahead with a robust returns policy because that is what the law and the country's best interest impose, in accordance with human rights," he said.
Greece was once the main points of entry to the European Union for migrants and asylum seekers from countries including Syria.
However, since the 2016 deal between the EU and Turkey, the number of migrants arriving on the shores of Greece has rapidly decreased.
Closures of the borders across the Balkans have resulted in migrants getting trapped in Greece, causing overcrowding in migrant camps.
Greece has come under fire for the living conditions in the camps by humanitarian organisations, with some operating at twice their capacity.