Dense fog in north India has thrown long-distance train schedules, both to and from Calcutta, haywire. Trains from Delhi and other parts of north India, including two Rajdhani Expresses, arrived in the city several hours behind schedule on Friday.

The railway authorities cancelled the Howrah-Kalka Mail and the Howrah-Delhi Poorva Express on Sunday and Monday, respectively, because of the delays.

Railway officials said the New Delhi-Sealdah Rajdhani Express arrived ten-and-a-half hours behind schedule and the Howrah Rajdhani was delayed by 10 hours on Friday. The Kalka-Howrah Mail was delayed by 15 hours and the Jodhpur-Howrah Express by eight hours.

Other trains were also delayed by seven to nine-and-a-half hours, the officials said. The stretch between Delhi and Dhanbad, a distance of around 1100km, has been the worst affected by fog. Trains were moving at an average speed of 20 to 25kmph because of poor visibility, said a railway official.

Although there was no fog at the Calcutta airport on Friday, some flights from Delhi were delayed because of dense fog.