Oil prices settled up about 9 percent on Thursday, at their highest in nearly four years, as Iran stepped up attacks on oil and transport facilities across the Middle East, and the country’s supreme leader vowed to keep the vital Strait of Hormuz shut. Brent futures settled at USD100.46 a barrel, up USD8.48, or 9.2 percent, after touching a session high of USD101.60. US West Texas Intermediate