** Oil & Natural Gas Corp Ltd's shares fall as much as 3.5 pct to 185.85 rupees - biggest intraday percentage drop since May 5

** Venezuelan state oil-firm PDVSA has not made debt payments to ONGC since April, sources tell Reuters


** PDVSA earlier used a Russian state-owned bank and Reliance Industries Ltd as intermediaries to make payments to ONGC

** PDVSA and ONGC Videsh - the overseas investment arm of ONGC - signed a deal last year under which PDVSA sells oil on behalf of ONGC and sends cash to the Indian firm


** Up to Wednesday's close, ONGC stock had risen 6.7 pct in 12 months