** Explorers Oil and Natural Gas Corp ONGC.NS, Oil India OILI.NS fall as much as 4.1% and 4.3%, respectively
** ONGC biggest loser on Nifty 50 index .NSEI, which is up 3.45%
** Oil prices slide below $100/barrel as a two-week Iran ceasefire sparks relief rally, fuelled by hopes that oil and gas flows through Strait of Hormuz could resume
** Easing oil prices negatively impact realisations, margins for upstream oil companies
** YTD, ONGC up ~17%, OILI up 8%
(Reporting by Urvi Dugar in Bengaluru)
((UrviManoj.Dugar@thomsonreuters.com;))