Mumbai, March 5 -- The rivalry between India's two stock exchanges is set to intensify, with the National Stock Exchange (NSE) shifting the expiry day for its weekly Nifty options contract to Monday from Thursday, starting 4 April. The move comes just a day before the weekly expiry of BSE's Sensex options, potentially cutting into BSE's trading volumes, which tend to peak on Mondays and Tuesdays.

A circular from NSE, issued after market hours on Tuesday, triggered a 5% fall in BSE shares to Rs.4,230 at the time of writing, even as benchmark indices Nifty and Sensex gained over 1% intraday.

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"The change of expiry day will hot up the competi...