State-run oil marketing companies increased petrol and diesel prices on Monday, marking a seventh straight day of hike in the fuel rates. With effect from 6 am on Monday, the price of petrol was at Rs. 73.91 per litre in Delhi, Rs. 76.60 per litre in Kolkata, Rs. 79.57 per litre in Mumbai and Rs. 76.83 per litre in Chennai, according to notifications from Indian Oil Corporation (IOC). Petrol prices were increased by up to 29 paise per litre in the Delhi, Kolkata and Mumbai, compared to the previous day's rates, data from Indian Oil showed. In Chennai, petrol rates were hiked by 31 paise per litre.