NEW DELHI, Jan. 5 (Xinhua) -- Air and train services have been severely hit in the Indian capital Friday as fog continued to wreak havoc in the city and adjoining areas since New Year.

Some 17 flights to and from Delhi's Indira Gandhi International Airport and over 100 trains have been affected due to dense fog that has enveloped the city since the early hours of the day, officials said.

"Some 17 domestic and international flights have been delayed to and from Delhi's Indira Gandhi International Airport owing to low runway visibility because of dense fog. The runway visibility has come down to less than 50 metres," a senior aviation official said.

Similarly, 62 trains have been delayed, 20 rescheduled and 18 cancelled to and from the two main railway stations -- New Delhi railway station and Old Delhi railway station, a senior Indian Railways official said.

Train services have been disrupted although the Indian Railways has installed fog-safety devices in all trains. "The fog-safety devices are meant to cut down delays," Northern Railway chief public relations officer Nitin Chowdhary said.

Since the beginning of New Year, the national capital has been hit by thick fog that has severely disrupted flights and trains, particularly during the morning time.

Fog is common in northern India, particularly in the winter months of December and January, and is responsible for many road accidents.