By Saikat Chatterjee LONDON (Reuters) – World markets were set for another tumultuous week after Western nations announced a harsh set of sanctions to punish Russia for its invasion of Ukraine and as fighting intensified for a fourth day. U.S. stocks have fallen nearly 8% so far this year, on track for the worst annual start since 2009, and worries over the intensifying conflict in Ukraine has shaken markets across the world. Though Wall Street ended higher on Friday with major indices up between 1.5%-2.5%, analysts expected markets to come under selling pressure on Monday. “Nobody likes uncer…