The move came late Thursday after over a dozen people in the Nea Smyrni settlement near Larissa, 354 kilometres (220 miles) north of Athens, tested positive for the virus.
"There will be tests throughout the area that is under lockdown," local governor Costas Agorastos told Proto Thema daily Friday, adding that screenings would also be carried out in other Roma communities in the area.
The country of 11 million has confirmed 1,955 coronavirus cases. Eighty-six people have died and another 79 are in intensive care.
The Greek government has reinforced highway and port controls to keep the public from travelling to the countryside and islands ahead of Orthodox Easter celebrations on April 19.