A thick layer of fog stretching from Punjab to Bihar reduced visibility across the Indo-Gangetic plains on Friday morning, with the India Meteorological Department (IMD) issuing a red alert for Delhi and warning that road, rail and air traffic may be affected. (Pics/PTI)

Delhi once again woke up to a thick layer of smog on Monday, as the air quality remained in the `severe` category across the National Capital Region (NCR), raising serious health concerns for residents. (Pics/PTI)