Nifty 50 falls 6.3% in September, worst monthly series in 25 years; what triggered the sell-off?

The Nifty 50 fell 6.3% in September 2026, marking its worst September series in 25 years, with only pharma among major sectors ending in the green. The sell-off was triggered by surging crude oil prices following US-Israel strikes on Iran, elevated global bond yields, persistent FII selling, and concerns over potential RBI tightening at the October meeting. The index also posted seven consecutive weekly losses, its longest losing streak since 2020, and is testing critical support at the 200-week moving average of 22,600.