NEW DELHI — A thick blanket of fog has engulfed Delhi and adjoining areas in northern India, leading to travel delays and chaos.

More than 100 flights were delayed at the Delhi airport on Friday morning, according to PTI news agency. Dozens of trains have also been rescheduled, or are running late.

India's weather department has said that foggy conditions are likely to continue for the next few days.

Dense fog is common at this time of the year in Delhi and other parts of northern India, as the region grapples with an intense cold wave.

Photos and videos showed several cities shrouded in dense mist and haze.

Around nine airports including the one in Delhi experienced zero visibility on Friday morning, the India Meteorological Department (IMD) said.

The Delhi airport has issued an advisory to passengers, warning them of significant delays.

"While landing and take-off continue at Delhi airport, flights that are not CAT III compliant may get affected," the airport said in a statement, referring to the radar system that enables automatic landings when there is very low visibility.

Several airlines have also issued statements urging travellers to check flight schedules before planning their journeys.

IMD considers fog "dense" if visibility drops below 200m and "very dense" if it falls below 50m.

The weather department has said that Delhi may experience light to moderate rainfall on 6 January, which is likely to further lower temperatures. — BBC