BENGALURU, July 1 (Reuters) - Indian shares on Friday began the second quarter on the back foot, hammered by heavy losses in Reliance Industries and ONGC after the government introduced export duties on oil products to boost domestic supplies.

The NSE Nifty 50 index was down 0.92% at 15,634.8 by 0631 GMT, while the S&P BSE Sensex slid 0.89% to 52,549.35, after falling up to 1.7% each earlier in the session.

The indexes, which on Thursday capped their worst quarter since the early days of the COVID-19 pandemic, are set to close the week marginally lower if losses hold.

India introduced export duties for gasoil, gasoline and jet fuel and imposed a windfall tax on oil producers that have benefited from higher global crude oil prices, sending energy stocks into a spiral.

Oil-to-retail conglomerate Reliance Industries, India's most valuable company, shed $19.35 billion in market value as its stock plunged as much as 8.7%, marking its biggest intraday slide since Nov. 2, 2020.

The Nifty Energy index fell 3.7% in its sharpest drop since mid-May.

State-owned oil producer ONGC plummeted 12.3% - its biggest slide since pandemic-wrecked March 23, 2020. Oil India slid 9%, while Mangalore Refinery and Petrochemical slumped 10%.

Meanwhile, jewellery makers Titan Company and Tribhovandas Bhimji Zaveri slipped 6% and 4.1%, respectively, after India raised basic import duty on gold to 12.5% from 7.5%.

The Nifty auto index slid 1.5%, ahead of monthly sales data, while the Nifty Bank index fell 1%.

The rupee hit a fresh record low of 79.11 against the dollar, versus Thursday's close of 78.97.

Elsewhere in Asia, stock markets got off to a shaky start on Friday as growth fears mounted. (Reporting by Chris Thomas in Bengaluru; editing by Uttaresh.V)