N'DJAMENA/BAMAKO (Reuters) - In Chad's scorching capital N'Djamena, housewife Sylvie Belrangar turned the handle of a tap but nothing trickled out as water shortages and extreme temperatures sweep parts of West and North-Central Africa's Sahel region.    "The president promised water and electricity. But since then, we've seen nothing," she said last week, surrounded by withered plants in her parched compound.    Belrangar's plight is echoed elsewhere in the semi-arid Sahel, whose worst heatwave in recent memory exposed in April the struggle of junta-led countries, such as Chad and Mali, to guarantee basic services when the need for water and electricity is most acute.

Recent outages have stoked frustration with the Malian and Chadian military authorities in some quarters, increasing social tensions when both countries stand at a political crossroads.     A presidential vote in Chad on Monday is expected to cement Mahamat Idriss Deby's grip on power following two years of rule after his father's death. 

Critics say the poll is a facade to legitimise Deby's rule and will not reflect the wishes of voters like Belrangar, who have lost faith in Deby's leadership.

"We have a president who can't even provide water and electricity, let alone anything else," she said. "Let the authorities listen to our cries."

Over 3,000 km (1,860 miles) west in Mali's capital Bamako, ice vendor Bintou Traore draped blankets over her dwindling ice stock on Tuesday to shield it from the sun.     "Ice is very expensive now," she said. "At the factory, prices have gone up because the plants run on generators."

The April heatwave led to a surge of excess deaths at Bamako's Gabriel Toure Hospital, with thousands of other likely victims across the region, according to climate scientists.

Maintaining a reliable power supply is key to curbing the fallout from extreme heat because it keeps fans, air-conditioners, and fridges running.

Officials from the governments of Chad and Mali did not respond to multiple requests for comment.

A rise in electricity outages in Mali since the military seized power in a 2020 coup has affected public support for the junta, particularly when the temperatures rise and people suffer, said political analyst Koureissi Cisse.    "People outside are having seizures and strokes. People are dying... because of the heat, but also lack of electricity," he said.

Opposition figures have pointed to the power cuts as an example of the junta's poor governance even as the authorities further delay a promised transition to democracy and move to limit political activities in the name of maintaining public order.

(Reporting by Mahamat Ramadane and Idrissa Sangare; Writing by Cooper Inveen; editing by Jonathan Oatis)

By Mahamat Ramadane and Idrissa Sangare