Two persons were killed and a dozen injured in three separate road accidents in Aligarh in Uttar Pradesh on Wednesday, police said. A dense smog has covered most parts of the state over the past two days.The first accident took place at the Khaireshwar roundabout around 8 a.m. when a truck collided with a tractor head-on, killing two people instantly.A second accident took place an hour later near the Allana Meat Factory on the Palwal-Aligarh highway where there was a pile-up of four vehicles. The accident left four injured. Eight persons were injured in the third accident on the new Aligarh bypass road in another pile-up of vehicles.