KARACHI: The Pakistan Stock Exchange (PSX) tumbled sharply and lost more than 5,400 points on Monday, the market data showed, amid escalating geopolitical tensions between the United States and Iran and a marked lack of investor risk appetite. The benchmark KSE-100 index 5,478 points, or 3.16 percent, to close at 167,691 points on Monday as compared to Friday’s close of 173,169 points, according to the PSX website. The development comes a day after US President Donald Trump said he would decide in “10 or 15 days” whether to order strikes on Iran if no nuclear deal is reached.