Argentina's capital, Buenos Aires, was hit by a major blackout that left more than a million homes without power and caused rush hour traffic jams.

Electricity also went off at the Congress building and presidential palace.

Power was back on in most districts by late Wednesday, Nov 7 evening. The electricity company said two high voltage lines had failed, amid record demand for energy after three days of high temperatures.

The blackout knocked out traffic lights and badly disrupted the metro system as people were heading home after work.

Electricity company Edesur said two high voltage cables had stopped working. Edesur spokeswoman Alejandra Martinez said that although the exact cause was not yet known, recent heavy demand had put a strain on the grid.

Buenos Aires has been sweltering for the past three days with temperatures of 33C.