Global stock markets extended their shakeout into a second day Tuesday, plunging amid worries that a possible US recession will cause a worldwide economic slowdown. The dramatic declines in Asia and Europe were expected to spread to Wall Street, where stock index futures were already down sharply hours before the trading day began. Japan's Nikkei 225 index, the benchmark for Asia's biggest bourse, was down 5.1 percent in afternoon trading after dropping 3.9 percent Monday. Trading was halted in India when the Sensex index plummeted 9.75 percent within minutes of opening. Hong Kong's Hang Seng index dropped 8 percent by midday after diving 5.5 percent the day before.