At least 21 people were killed and a number of others injured in two separate road accidents on Tuesday in the northern and southern parts of the country, the local media reported.According to a spokesperson for the National Highways and Motorways Police, at least 14 people were burnt to death and six others were injured when a passenger van caught fire after colliding head-on with a trailer in Rawalpindi city in Pakistan's Punjab province.Fire brigade officials reached the scene soon after the accident and doused the fire, said rescue officials.The injured were shifted to the Pakistan Institute of Medical Sciences in Islamabad, where several of the injured were reported to be in critical condition, Xinhua news agency reported.The ill-fated passenger van was coming from Jhang, a district in Punjab, to Rawalpindi when the accident happened. The motorway police said the identities of the deceased passengers were yet to be determined.In another accident, which happened at about 7.30 a.m., at least seven people were killed and five others sustained injuries in a collision between a passenger van and a truck-trolley in the country's southern port city of Karachi.Rescue teams and police reached the spot after the accident and shifted the bodies and injured, who included women and children, to a nearby hospital where the condition of two of the injured was reportedly critical.According to initial investigations, over-speeding was the cause of both accidents.