Sensex dipped 319 points to end at 77,186.74 on Monday while Nifty plunged 121 points to close at 23,361.05 as Indian rupee fell below 87 against US dollar for first time. US President Donald Trump's tariffs on Canada, Mexico and China also sparked fears of a broader trade war. FII outflows and RBI's upcoming MPC meeting further made investors cautious.