Petrol and diesel prices were increased by up to 91 paise per litre on Saturday, the third increase in less than 10 days.Petrol price has been increased by 87 paise in Delhi from Rs 98.64 to Rs 99.51 per litre. Diesel rates have gone up by 91 paise from Rs 91.58 to Rs 92.49.This is the third increase in rates since May 15, when state-owned oil companies started passing on the elevated energy prices arising from the West Asia conflict in a calibrated manner.Prices were hiked by Rs 3 a litre on May 15, followed by a 90 paise increase on May 19. In all, rates have gone up by almost Rs 5 per litre.