Ecuador suffered a nationwide blackout Wednesday as the electrical grid failed, Energy Minister Roberto Luque said.

"There is a breakdown in the transmission line, which caused a chain of disconnections, so nationwide there is no electricity," Luque said on X. 

But power started returning gradually, at least in the capital Quito, about an hour later, AFP observed.

The blackout was abrupt, surprising Quito's subway riders as trains came to a halt and thousands of people had to be evacuated.

Traffic lights stopped working, and police manned intersections to maintain some semblance of order in the city of three million.

"The incident must have been major because it even knocked out power to the metro, which has its own separate system," Quito Mayor Pabel Munoz said on X.

Traffic chaos also hit the big Pacific port city of Guayaquil, an AFP correspondent observed, and people became stranded in elevators in office and residential buildings.

Street cars in the southern city of Cuenca stopped running.

Luque said he would give a press conference later Wednesday on the blackout.

Ecuador suffered planned rolling blackouts in April because drought has left water levels low at ageing hydroelectric power facilities.

This spotty service ended in May when the rainy season arrived.