A fault at Isinya substation caused the massive power outage that affected the entire country on Thursday.

The Kenya Power and Lighting Company (KPLC) said that in a statement issued on Thursday evening while confirming the restoration of power supply to parts of the country.

"We have restored power supply to customers in parts of Western, South Nyanza, North Rift, Central Rift and Nairobi," the statement read.

"The cause of the system disturbance has been identified and is being addressed by KETRACO engineers, while our technical teams are working on the restoration of power supply to the rest of the country."

In a subsequent statement issued later on, Kenya Power confirmed it has restored power supply to all parts of the country and once again apologised to its consumers for the inconveniences the outage caused.

"We are glad to report that normal power supply has been restored to all parts of the country," the statement read.

"We thank our customers for their patience and apologise for the inconvenience caused by the outage."

Kenyans from across the country have complained bitterly over the power outage, saying it has affected their businesses.

The power outage came as several football lovers are keenly following the World Cup football competition.

This is the second serious power outage to occur in the country within less than a month.