Victoria state has been hit by devastating bush fires this summer
Massive power cuts and soaring temperatures have caused havoc in the Australian state of Victoria.
Electricity supplies to about 200,000 people were hit after a bushfire knocked out power lines linking Victoria to the national grid.
In Melbourne, trains and trams were affected and more than 1,000 traffic lights failed, causing chaos on roads.
The outages happened at a time of high demand as people used air conditioners to cope with 39C heat.
"There are power outages across Victoria from the border with New South Wales state to Melbourne," a state police spokesman told Reuters. "The cause is bushfires and heavy demand. It's a stinking hot day and the demand is overloading transformers."
It is not clear when power supplies will be restored to normal.
In Melbourne, Australia's second-biggest city with 3.4 million residents, hospitals lost power and shops and offices were forced to close.
During rush-hour, massive traffic jams occurred after 1,200 traffic lights in the city and nearby Geelong metropolitan area stopped working.
Police directed traffic by hand, appealing for drivers to take extra care.
"We are asking people to take all due care at intersections with traffic lights out, and we are asking them to be patient," Victoria Police spokesman Senior Constable Wayne Wilson said.
Commuters using public transport fared no better as the city's famous trams ground to a halt and trains were slowed.
"While riding my bike home through Brunswick the traffic lights were down, and so there was quite a lot of confusion at the major intersections. I stopped at a shop, but they couldn't make any sales, because their cash registers weren't operating," said BBC News website user Ben Butcher.
Along with a series of blackouts, in which all electricity supplies are cut, some areas experienced brownouts, in which voltage drops, causing lights to dim.
A spokeswoman for transport company Connex said trains across the suburban network were running, but not at their usual rate:
"They're running very slowly, we've got low voltage coming through," Kate De Clercq said. "There are chances of massive delays, rather than cancellations."
Both landline and mobile telephone networks also jammed as the disruption caused a sudden spike in calls.
The heat also disrupted play at the Australian Open tennis competition, which is being played in Melbourne, though organisers said the venue still had power.
Local media said a bush fire near Benalla, in the north-east of the state, had been the cause.
Bushfires are common in Australia's summer, but officials say the situation is even worse than normal this year, because of a long-standing drought.
Many fires are caused by lightning, while others are started deliberately.