LONDON, April 20 : Oil prices jumped around 5 per cent in early Monday trading on fears that the ceasefire between the United States and Iran could collapse after the U.S. seized an Iranian cargo ship and traffic through the Strait of Hormuz remained largely halted. Brent crude futures advanced $4.19, or 4.6 per cent, to $94.57 a barrel by 1027 GMT and U.S. West Texas Intermediate was up $4.60, or 5.5 per cent, at $88.45. Both contracts tumbled by 9 per cent on Friday, their largest daily