The Health Ministry on Thursday warned elderly Athenians as well as those suffering from breathing problems to remain indoors due to high levels of pollution in the city.
At 3 p.m. on Thursday, a weather station in Thrakomakedones, northern Athens, recorded ground level ozone at 209 mg/m3 when the warning limit is 180 mg/m3.
The ministry also advised parents to keep their children from engaging in intense physical activity.
The rise in pollution has coincided with increasing temperatures.
The current mini heat-wave is expected to last until the end of the week.