July 15 (Reuters) - Australian shares snapped a three-session rally on Friday, as weakness in commodity prices weighed on mining and metal stocks, with mining major Rio Tinto tumbling after flagging a hit to its second-half earnings on inflation woes.

The S&P/ASX 200 index shed as much as 1.7% at 6,537.2 by 0106 GMT. The benchmark has lost over 1.7% this week, its biggest weekly drop in four.

Leading the decline, local miners tanked as much as 3.9% to hit their lowest since September 2021, as iron ore prices slipped on demand fears in China.

The sub-index is set to lose for six straight weeks, giving up 6.5% in value this week. BHP and Fortescue Metals lost 3.7% and 5.2%, respectively.

Rio Tinto receded more than 3%, losing more than 5% this week. The miner said it was facing labour shortages in Western Australia and warned that rising inflation would impact its underlying earnings in the second half of the year.

Financials, one of the top-weighted sectors on the benchmark, slumped as much as 2%. The country's 'big four' banks fell between 1% and 3%. The sub-index has lost 1.8% this week.

Gold stocks fell 2.6% to their lowest since October 2018, as strength in the U.S. dollar dented prices of the commodity. The sub-index slumped 3.5% this week.

Sector leaders Northern Star Resources and Newcrest Mining lost 2.5% each.

Energy stocks shed as much as 1.7%, with sector majors Woodside Energy and Santos weakening 0.4% and 0.6%, respectively.

Bucking the trend, shares in domestic carrier Regional Express jumped 3.7%, after the company said its unit would buy aviation operator Cobham's fly-in fly-out business National Jet Express.

New Zealand's benchmark S&P/NZX 50 index slipped 0.3% to 11,156.64 and is set to lose over 0.1% in value this week.

($1 = 1.4826 Australian dollars) (Reporting by Roushni Nair in Bengaluru; Editing by Rashmi Aich)