Hundreds of farmers blocked major highways, including National Highway 1 linking Delhi with parts of Haryana and Punjab, on Friday following a nationwide call by farmers' unions to demand loan waiver and enhanced MSP for produce.The farmers blocked NH 1 near the Anaj Mandi (grain market) at Ambala in Haryana, around 45 km from here.The protesting farmers parked their tractors on NH 1 and squatted on the road despite the sweltering heat."We have blocked the highway to protest against the policies of the central government. We will keep the highway blocked for three hours. We are protesting peacefully and we will not budge till the central government accepts our demands," Haryana Kisan Union President Gurnam Singh said.In neighbouring Punjab, farmers blocked traffic near the industrial town of Phagwara near Jalandhar, around 130 km from here.There were reports of other highways being blocked by the farmers in Haryana and Punjab. Heavy police presence could be seen at various places in Haryana and Punjab to maintain law and other in view of the protest by farmers.The police diverted traffic at several places as the farmers blocked the highways.The opposition Congress in Haryana held a rally in Kurukshetra on Friday to support the farmers.The farmers are demanding implementation of the Swaminathan Commission report on the agriculture sector, loan waiver for debt-ridden farmers, enhanced Minimum Support Price (MSP) on crops and acceptance of other demands.