The European Union's border agency is to offer more assistance to Greece in controlling illegal migration.
Last month 175 armed guards were sent by Frontex to Greece's border with Turkey because of a surge in the number of illegal crossings.
Frontex uses thermal imaging cameras, which are most effective at night, when most migrants cross.
About 350 people per day crossed the border before the EU team began its mission en route to Britain, France or Germany. Now, the BBC reports, around 60 people per day make it.
The region most affected is North Evros. Area police chief Colonel Georgios Salamagkas says 35,000 migrants had been arrested since the beginning of the year.
That is the equivalent to the population of the villages in that region.
Human rights organisations are voicing concerns about conditions in detention centres where many migrants are held.
The UNHCR refugee agency has described the conditions as a humanitarian crisis.