Police said three persons were killed and four others injured as several vehicles collided in Rohtak along the Rohtak-Gohana road.
Among the vehicles which rammed into each other included an oil tanker, a truck, a van, jeep, and few cars, police said, adding the accident occurred near Ghilor village, about 70 km from Delhi.
In another accident, over 70 vehicles were involved in multiple collision in Karnal district that left a woman dead and at least 50 others injured.
They said that due to fog and smoggy conditions, the visibility had dropped considerably on entire stretch of the highway in Karnal and surrounding areas including Panipat and Sonepat.
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Police said both at Rohtak and Karnal the injured were immediately shifted to hospitals.
The accidents caused traffic jams on the road and police said efforts were stepped up to clear the vehicles which were involved in the accidents.
On the Karnal-Delhi highway, many people could be seen having parked their vehicle along the road side waiting for the visibility levels to improve.
Director of the Chandigarh's Met Department, Surinder Paul told PTI today that there can be variety of reasons behind fog making an early appeareance this season in some parts.
He said fog which is seen in some parts can become worse when it gets mixed with smoggy conditions, escalating the problem further.
Paul also said that as there was not much wind movement during past few days, it had led the situation remain static.
states which have imposed a ban on burning of paddy residue, have been urging farmers not to burn crop residue which causes smog and other serious halth risks.
However, many farmers in Haryana and the neighbouring Punjab have continued with the practice.
Despite the warnings, during the past three weeks, reports from various areas in Haryana and Punjab, suggest that farmers have continued to burn paddy straw.
Punjab Chief Minister Parkash Singh Badal told reporters today that "we keep telling them (farmers) not to burn the residue. We have given them machines, but some of them still make mistake.."
Notably, farmers are also being provided subsidy on farm implements like happy seeder, rotavators, straw reapers for managing straw in a sustainable manner.
In the last few years it has been noted that when stubble is burned in the two leading agrarian states, the pollutants enter Delhi, adversely affecting the air quality in the national capital.
Burning of paddy residue causes air pollution, smog and also poses a serious threat as it leads to medical problems such as breathing issues, allergies and asthma attacks.