Dec 23 (Reuters) - Australian shares extended gains on Thursday, led by banks and gold miners, as a study helped ease concerns about the severity of the Omicron coronavirus variant, while Bega Cheese slumped on forecasting earnings outlook below analyst estimates.

The S&P/ASX 200 index rose 0.2% to 7,380.1 by 0030 GMT and was headed for a third straight session of gain.

A South African study suggests reduced risks of hospitalisation and severe disease in people infected with the Omicron variant compared to Delta, but World Health Organization officials cautioned that it was too soon to draw firm conclusions.

Heavyweight financials climbed as much as 0.7%, driven by gains in the so-called "Big Four" banks.

Gold explorers were among the top gainers in the bourse, rising as much as 2.2% to their highest since late November on the back of a surge in bullion prices.

Newcrest Mining rose 0.8%, while Northern Star Resources jumped more than 2% to hit a three-week high.

Mining stocks pared early gains to trade flat, as iron ore prices remained weak on demand concerns in top producer China.

Meanwhile, Bega Cheese tumbled to a more than four-month low after the company warned of a hit to its 2022 fiscal earnings from strong competition for dairy supply in Australia, high global prices and the coronavirus impact.

The company's shares dropped as much as 9.3% to post their biggest intraday loss since March 16, 2020.

Healthcare stocks were set for a fourth straight session of gain, while energy stocks rose 0.4% on firmer oil prices.

Major indexes on Wall Street notched strong gains overnight in a broad rally, benefiting from upbeat economic data.

New Zealand's benchmark S&P/NZX 50 index was up 0.1% at 12,883.84. (Reporting by Harish Sridharan in Bengaluru; Editing by Subhranshu Sahu)