JAKARTA - Indonesian President Joko Widodo has chastised state-owned electricity company PLN for the massive blackout that hit Jakarta and its neighbouring provinces on Sunday (Aug 4).

"With whatever means, the electricity must be restored in areas that have yet to recover," he said on a visit to the company's headquarters on Monday, adding: "Such a major incident should never happen again."

The blackout, which PLN said was caused by disruption in two extra-high voltage power transmission circuits and began at 11.48am Jakarta time, prompted lights to go out for up to eight hours in the capital, Banten, West Java, and Central Java.

In some areas power had not been restored more than 24 hours later.

Mr Joko questioned why PLN management did not have risk governance and back-up strategies so that it could address the trouble immediately.

"We know this did not only damage PLN's reputation, but also affected many other elements outside PLN, especially consumers that were at loss," he said in a statement.

"It was very dangerous, for instance, for public transport services like the MRT."

Mr Joko called for PLN to fix the problem as soon as possible.

PLN's acting president director Sripeni Inten Cahyani responded by explaining that the company did not anticipate simultaneous disruptions at two of its four power transmission systems when another was under regular maintenance - meaning only one was operational.

"We apologise for the slow process. We admit the process has been snail-paced," she said, adding that the company is still probing the incident.

The company, which has estimated a Rp 90 billion (S$8.7 million) loss as a result of the incident, also promised to compensate affected residents by cutting power tariffs in line with the duration of blackouts.

But it said it still could not fully restore electricity as soon as expected as its power supply will only recover gradually.

On Monday, PLN carried out blackouts alternately in greater Jakarta and Bandung.

Alternate blackouts are common outside Java and Bali, as the world's largest archipelago has not been able to cope with surging power demand.

Although activities in the capital apparently ran smoothly, a number of residents, especially in areas on the outskirts of Jakarta like Tangerang, said they had struggled with the blackout since Sunday morning.

A resident of Bintaro in South Tangerang, Banten, who identified himself only as Zul, said his neighbourhood was without power from at 11am on Sunday until Monday afternoon, other than for a five-minute spell late on Sunday.

"Residents here start to panic because they cannot get water... A number of them are going to public places, such as a mosque that has generators, to take water," he told Elshinta radio.

The continuing blackout prompted people to take showers in offices or malls, while businesses - both small and big - were affected.

The blackout is the worst to affect Indonesia since a partial blackout across Java and Bali in 2008.

It caused chaos in the streets of Jakarta and neighbouring city of Bandung, paralysing traffic lights and public transport, as well as mobile phone and banking services.

Travellers were stranded at train stations, while some people chose to stay at hotels which had power.

Indonesian Retailers Association chairman Roy Mandey estimated that the blackout, which affected 82 shopping centres and more than 2,500 stores, could generate Rp 200 billion (S$19million) in losses.

"People were reluctant to shop or cancelled shopping," he said.