New Delhi" After a brief spell of relief from the biting cold, the national capital recorded a cold morning on Sunday and dense fog engulfed northern regions affecting train and flight operations due to low visibility.


Six flights were delayed from Delhi's Indira Gandhi International Airport (IGI) due to fog and lower visibility, according to the airport authority on Sunday, reported news agency ANI.


Among the flight routes affected by the severe fog were Delhi-Riyadh, Delhi-Shimla-Kullu, Delhi-Varanasi, Delhi-Dharamshala-Srinagar, Delhi-Shimla- Dharamshala, Delhi-Dehradun.


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Almost 20 trains were running late on Sunday as dense fog engulfed most of North India. Among the trains delayed include Darbhanga-New Delhi Clone Special, Puri- New Delhi Purushottam Express, Gaya- New Delhi Mahabodhi Express, Malda Town- Delhi Farakka Express, Barauni-New Delhi Clone Special, Banaras-New Delhi Kashi Vishwanath Express, Dibrugarh Town New Delhi Rajdhani Express, Sai Nagar Shirdi Terminus-Kalka Superfast Express, Kamakhya-Delhi Brahmaputra Mail, Katihar-Amritsar Amrapali Express.


According to officials of Northern Railway,  all the above trains are running late by up to 2 hours.


"Raigarh-Hazrat Nizamuddin Gondwana Express, Visakhapatnam-New Delhi Andhra Pradesh Express, Ayodhya Cantt-New Delhi Express, Rajgir-New Delhi Shramjeevi Superfast Express, Raxaul- Anand Vihar Terminal Sadbhavana Express, Jabalpur-Hazrat Nizamuddin Gondwana Express, Manikpur-Hazrat Nizamuddin Uttar Pradesh Sampark Kranti, MGR Chennai Central -New Delhi Grand Trunk Express, MGR Chennai Central -New Delhi Tamil Nadu Express, Hyderabad Deccan Namoally -New Delhi Telangana Express are also running late by 2 hours," Northern railways added.


The satellite imagery and available visibility data from the India Meteorological Department (IMD), showed a layer of fog extended from Punjab and adjoining northwest Rajasthan to Bihar across Haryana, Chandigarh and Delhi and Uttar Pradesh.


Delhi's Safdarjung recorded a minimum temperature of 5.6 degrees Celsius around 6.10 am. According to the Meteorological department, the visibility in Palam was recorded at 200 meters at 6.10 am.


India Meteorological Department (IMD)  observed dense to very dense fog over parts of Punjab, Northwest Rajasthan, Jammu division, Haryana, Chandigarh and Delhi, Uttar Pradesh, Bihar and Tripura.


"Dense/Very Dense Fog layer (in the white patch) extends from Punjab to Bihar across Haryana, Delhi and Uttar Pradesh," tweeted the India Meteorological Department. Meanwhile, IMD has issued an orange alert for dense fog and chilly conditions in neighbouring Punjab and Haryana on Sunday and Monday.