Prime Minister Kyriakos Mitsotakis said the cabinet had discussed plans to make water companies more "viable", noting that reserves in Athens were down 50 percent compared to three years ago.

There will be additional use of desalination technology and water reuse, the premier's office said, adding that Greece globally ranked 19th in terms of drought risk.

The National Observatory of Athens recently warned that, following high temperatures and low rainfall in June, almost all of Greece displayed above-normal drought levels for this time of year.

Temperatures continued to rise Wednesday in a heatwave expected to last until Sunday.

Between 40C and 44C are expected on Wednesday in the eastern, central, and northern inland regions, as well as on the islands of the eastern Aegean Sea, according to the meteo.gr website of the Athens National Observatory.

In Athens, the heat reached 36.3C around 1:30 pm (1030 GMT). It is expected to rise to 42C on Thursday according to meteo.gr.

To protect visitors and guards, Greek authorities have closed the Acropolis in Athens during the hottest hours of the day, between 1:00 pm and 6:00 pm, until Friday.

- 'The asphalt is boiling' -

The Greek government has also banned outdoor work in several sectors during the hottest hours to minimise health risks.

"It's inhumane to work in such conditions. The asphalt is boiling," Panagiotis Arvanitidis, 35, a member of the food delivery workers' union in the Thessaloniki region (north), told AFP.

"The ambient temperature in my home over the past two days has exceeded 30C," said 50-year-old medical saleswoman Anna Spania.

"Without air conditioning, survival is impossible!" she added.

The heatwave's highest temperatures so far were recorded on Tuesday at Tragana, central Greece, at 44.9C, according to meteo.gr.

A Mediterranean country accustomed to intense summer heatwaves, Greece last year experienced its hottest summer on record.