Power is being gradually restored across Sri Lanka after a nationwide outage left buildings including hospitals having to rely on generators.

Officials say it may take a few hours to get power back across the island nation, but medical facilities and water purification plants have been given priority.

Energy Minister Kumara Jayakody reportedly blamed a monkey for causing the power cut, saying the animal came into "contact with our grid transformer causing an imbalance in the system", according to the AFP news agency.

The Ceylon Electricity Board (CEB) said the power cut had been caused by an emergency at a sub-station, south of Colombo, and gave no further details.

"Engineers are attending to it to try and restore the service as soon as possible," the minister said.

The CEB said "we are making every effort to restore the island-wide power failure as soon as possible".

Hospitals and businesses across the island nation of 22 million people have been using generators or inverters.

Sri Lanka experienced widespread blackouts during its economic crisis in 2022.