Gas prices went up slightly last week on average across Arizona. Triple-A Arizona says the average price at the pump is $2.88 a gallon, which is two-cents a gallon higher than last week. Spokesman Aldo Vazquez says the reason for the rise is due to oil prices. “Crude started to see some upward movement this week, which would translate to small increases at the pump by the end of April,” says Vazquez. In Flagstaff, gas prices were also up two-cents a gallon this week to $3.15 a gallon on average. In Prescott, gas is up a cent this week to $3.07 a gallon. Gas stations in both cities are selling gas for $2.99 a gallon and lower.