Global growth worries, U.S. government shutdown threat hit stocks

LONDON (Reuters) - World stocks extended a steep sell-off on Friday as the threat of a U.S. government shutdown and further hikes in U.S. borrowing costs compounded investor anxieties over the trajectory of global economic growth.E-Mini futures for the S&P 500 were off half a percent, indicating a lower open on Wall Street. Nasdaq futures were down 0.6 percent. European shares traded in negative territory, following in the footsteps of U.S. and Asian markets. The pan-European STOXX 600 fell..