A massive electricity outage hit Jakarta and some neighbouring provinces in Java yesterday, following problems at multiple power stations.
Public transport and banking services were widely disrupted, while traffic was thrown into chaos in some locations.
Disruption to the Ungaran and Pemalang power transmission system caused "power transfer from east to west" to fail, resulting in electricity tripping out at power plants in central and western parts of Java, state-owned electricity company PLN said in a statement.
This resulted in a blackout in Jakarta, Banten and West Java.
PLN's acting president director Sripeni Inten Cahyani apologised and said in a statement that the company had "taken maximal attempts" to avert the power cut, adding that it would conduct an internal evaluation.
The company said at 5.30pm local time (6.30pm Singapore time) yesterday that it would take six hours to recover the power system across Banten and West Java.
As at 9pm, power had been restored to most parts of Jakarta.
Residents in areas including South Jakarta, Bekasi and Tangerang told Radio Elshinta that electricity had been restored after 5pm.
In Jakarta, home to around 10 million people, the blackout affected public transport, cellphone and banking services. Heavy traffic jams were observed there and in Bandung, a three-hour drive away.
Meanwhile, some passengers on Jakarta's recently opened MRT system reportedly panicked and evacuated four train carriages which had suddenly stopped working.
Mr Muhamad Kamaluddin, the corporate secretary of operator PT MRT Jakarta, said in a statement that the company had stopped receiving power supply from PLN at 11.50am.
The operation of the LRT system linking areas in greater Jakarta was also halted because of the outage.
Many passengers on the network - which covers Jakarta and the nearby cities of Bogor, Depok, Tangerang and Bekasi - were stranded in train stations.
Ms Wiwik Widayanti, the president director of PT Kereta Commuter Indonesia (KCI), which operates the commuter train network, told Metro TV that it had cancelled more than 200 journeys in the hours after the blackout.
She said KCI was working with the operator of the Transjakarta bus network to help passengers get around.
KCI typically serves more than 880,000 passengers during weekends.
Some motorists used cash instead of cards to pay tolls as two unmanned toll gates stopped functioning, according to toll road operator PT Jasa Marga. Some Transjakarta bus passengers also used cash after fare payment machines went off.
The power cut also affected traffic lights, paralysing some roads - particularly in southern and western Jakarta.
Shopping malls, offices and apartments in Jakarta, which operate their own generators, managed to switch on lights and air-conditioning soon after the outage started.
A shopkeeper at a central Jakarta mall told The Straits Times that the power was cut off for only three minutes before returning to normal.
A 60-year-old shopper, who lives in Tangerang and gave his name only as David, said he and his wife spent longer than they had planned at the mall as a result of the blackout.
"It's hot in my house without the electricity. It's better to hang out here," he told The Straits Times.
The power outage also affected cellphone and ATM services.
Customers of major telecommunication operators Telkomsel and Indosat Ooredoo were temporarily unable to make calls or connect to the Internet, while some ATMs in South Jakarta stopped working, according to local media.