A heatwave in Morocco has killed at least 21 people in a 24-hour period in the central city of Beni Mellal, the health ministry announced on Thursday.

The meteorology department said soaring temperatures affected much of the North African country from Monday to Wednesday, reaching 48 degrees Centigrade (118 Fahrenheit) in some areas.

In Beni Mellal, "the majority of deaths involved people suffering from chronic illnesses and the elderly, with high temperatures contributing to the deterioration of their health conditions," the regional health directorate said in a statement.

Morocco has suffered a sixth consecutive year of drought and record heat this winter, with the month of January the hottest in the country since 1940, according to the meteorology department which had recorded temperatures approaching 37C in some places.

The rising temperatures and prolonged drought, which has lowered reservoir levels, are a threat to the vital agricultural sector.

Water evaporation reached 1.5 million cubic metres per day, Water Minister Nizar Baraka said at the end of June.

Morocco's record temperature -- 50.4C -- was set in August last year in Agadir, in the south of the country.

Scientists have linked climate change to more prolonged, stronger and more frequent extreme weather, including heatwaves. (AFP)