Oil prices rose on Monday after Yemen's Iran-backed Houthis launched missile and drone strikes at Riyadh on Saturday, escalating tensions in the Middle East while the United States and Iran remained in stalemate. Brent crude futures climbed 81 cents, or 0.78%, to $104.68 a barrel by 2202 GMT. U.S. West Texas Intermediate crude rose 76 cents, or 0.76%, to $101.06 a barrel.