Indian stock markets opened sharply lower amid tensions between US and Iran and concerns over crude oil supply through Strait of Hormuz. The Sensex plunged 808 points to 73,844, while Nifty 50 slipped 68 points to 23,416. Bank Nifty also declined 455 points. The rupee weakened by 21 paise to 95.51, reflecting a broad risk-off mood across global markets today.