The Syntagma metro station in central Athens will close at 12 noon on Thursday, the Greek Police (ELAS) has said.
The decision is part of security measures for policing marches and rallies marking the 10th anniversary of the killing by a policeman of teenager Alexis Grigoropoulos in the downtown district of Exarchia in 2008.
ELAS has ramped up its presence across central Athens, as well as in other cities where protest marches as being planned.
In the capital, one rally by students will take place at 12 noon and another by far-left groups at 5.30 p.m. Both are expected to cause significant traffic and transportation problems.
Parts of the downtown Thessaloniki were also closed on Thursday for a rally scheduled to start at noon.