Petrol price crossed the Rs 100-a-litre mark in Delhi following a fuel price hike on the back of firming international oil rates. It has increased by 35 paise per litre and costs Rs 100.21 per litre, while diesel rates were increased by 17 paise a litre and settled at Rs 89.53 a litre , according to a price notification from state-owned fuel retailers. This is the fourth increase in petrol prices this month.