An intruding monkey at a Sri Lankan electrical grid sub-station caused a general island-wide blackout on Sunday, government officials said.

The power outage, which began around 11:30 am (0600 GMT), had yet to be fully restored after three hours.

"A monkey has come in contact with our grid transformer causing an imbalance in the system," Energy Minister Kumara Jayakody told reporters.

The intrusion took place in a south Colombo suburb, he said.

While power was restored in some areas, it was not immediately clear how much longer the outage would last.

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

Sri Lankans had to endure months electricity blackouts in the summer of 2022 when the country plunged into an economic crisis.

Fuel stations ran out of petrol and diesel, forcing thermal power stations to ration electricity to 13 hours each day.