Four trains were cancelled and 27 delayed, the Northern Railway said in a statement.
Earlier Thursday, the capital woke to a thick blanket of fog. Visibility dropped to less than 300 metres in some parts of the city at 8.30 a.m.
Dense fog is expected Friday morning too.
The national capital has been witnessing dense fog since Monday. The Met office has said that the people of Delhi will not find respite from fog for a few days.
Thursday's maximum temperature was 22.4 degrees Celsius, normal for this time of year. Minimum temperature settled at 10.8 degrees Celsius, three notches above normal.
According to the India Meteorological Department, Friday's maximum and minimum temperatures are likely to be around 22 and nine degrees Celsius, respectively.
--IANS (Posted on 19-12-2013)