SYDNEY • Hundreds of thousands of people sweltering through a brutal heatwave in southern Australia were left without power yesterday, as the grid struggled with surging demand.

The authorities said about 60,000 customers were experiencing blackouts after it ordered forced outages to reduce the risk of the entire grid failing.

"We have asked for 100MW of involuntary load reduction, we have notified the networks, they're in the process of doing that," Australian Energy Market Operator chief executive Audrey Zibelman said.

The disruption comes as temperatures in Melbourne soared to 42.8 deg C just after lunch, before the mercury dropped 12 deg C in just seven minutes in the city in the early afternoon.

There were reports of up to 100 traffic lights without power in Melbourne, and some shops and cafes were forced to close. But the extreme heat did not deter tennis fans, who flocked to the Australian Open tennis semi-finals.

In other parts of Victoria state, the authorities had issued fire warnings, with hundreds of emergency services personnel and dozens of planes and helicopters on standby, as temperatures in some areas were expected to soar to 47 deg C.

Australia is reeling from a heatwave that peaked in South Australia on Thursday when the state capital Adelaide topped 47.7 deg C, breaking a 1939 record.

Meanwhile, the authorities farther south, on the island state of Tasmania, continued to battle bush fires.

The record-breaking heatwave has led wholesale power prices in Victoria to hit the market cap of A$14,500 (S$13,980) per MWh before midday yesterday, earlier than expected, and were forecast to remain there for the rest of the day, National Electricity Market data showed.

AGENCE FRANCE-PRESSE, REUTERS