LAGOS — Petrol prices have risen as the Dangote refinery increased its gantry price by a total of N100 per litre between 21 and 29 August, and pump prices in Lagos reached N1,310 to N1,320, a survey by Daily Trust found. The refinery is considering restricting supply to marketers who also import petrol, alleging that they blend imported products with its fuel. One marketer described the plan as a move towards monopoly. Professor Wumi Iledare said the allegations should be verified independently, while the NMDPRA said product quality is the regulator's responsibility.