The global rout resulting from tensions over the North Korean nuclear standoff continued on Friday as world stocks tumbled for the fourth day, on course for their worst week since November following a third day of escalating verbal exchanges between Trump and Kim, as European and Asian shares tumlbed, volatility spiked, and the selloff in US futures continued albeit at a more modest pace as the escalating war of words over North Korea drove investors on Friday to safe havens such as the yen, Swiss franc and gold.