* Australia warns virus outbreak will take weeks to tame
* Mining sub-index hits highest level since August 2011
* "Big four" banks down over 1%
By Arundhati Dutta
July 20 (Reuters) - Australian shares slipped on Monday after authorities warned that a surge in COVID-19 cases in the country's second most populous state could take weeks to tame.
The S&P/ASX 200 index .AXJO fell 0.3% to 6,018.5 by 1251 GMT, dragged by energy and financials stocks, after a 0.4% gain last week.
Australia's acting chief medical officer said the coronavirus outbreak in Victoria state could take weeks to subside despite a lockdown and orders to wear masks in Melbourne. respiratory disease caused by the novel coronavirus has flared up in Victoria in July, mainly in Melbourne, with a daily record of 438 new cases detected on Friday.
The energy sub-index .AXEJ led the fall on the benchmark stock index with a 2% drop as oil prices dipped. Woodside Petroleum WPL.AX , Santos STO.AX and Oil Search OSH.AX slipped between 2.1% and 3.2%.
The financial sub-index .AXFJ slipped 1.3% and was headed for its worst day in nearly two weeks, with all the "big four" banks down more than 1%.
However, South32 S32.AX , the world's largest manganese ore producer, said it would book a near $100 million impairment charge on its manganese alloy smelters, sending its shares down over 3% in early trade.
The metals and mining sub-index .AXMM rose 1.3% to its highest level since August 2011.
Resolute Mining RSG.AX was the top percentage gainer on both the sub-index and the benchmark with a 6% jump, after a new plan for its Mako gold mine extended the mine life and total gold production estimates. of Rio Tinto (LON:RIO) RIO.AX climbed as much as 0.8%, still riding on robust second-quarter iron ore shipments reported on Friday. New Zealand, the benchmark S&P/NZX 50 index .NZ50 rose 0.14% to 11,599.9 by 1251 GMT, with Chorus Ltd CNU.NZ adding 2.6%, while Contact Energy Ltd CEN.NZ gained 2%.