Lucknow, Feb 4 (IANS): Most parts of Uttar Pradesh were on Monday engulfed in a blanket of dense fog, disrupting vehicular, train and air traffic and throwing normal life out of gear.

According to the Regional Met Office, the fog will remain for a few days and cold wave conditions were likely to intensify over the week.

The sudden return of the cold wave was attributed to heavy snowfall in Uttarakhand, Jammu and Kashmir and Hiamchal Pradesh.

Most parts of the state, including western districts and those falling under the National Capital Region (NCR) -- Ghaziabad, Noida and Greater Noida -- saw visibility dip to less than 50 metres earlier in the day.

Traffic was hit in Kanpur, Lucknow, Varanasi, Agra, Prayagraj.

Rail traffic was also affected with more than a dozen trains of the Northern Railway (NR) and the North-Eastern Railway (NER) running behind schedule.

Lakhs of pilgrims, devotees and seers braved the intense cold in Prayagraj to take the holy dip in the Sangam at the ongoing Kumbh Mela on occasion of the "Mauni Amavasya".

Officials at the Chaudhary Charan Singh International Airport in Lucknow confirmed the delay in "all in-bound morning flights".