Morning traffic during heavy fog in Delhi, India December 1, 2016. Photograph: (Reuters)
North India, and in particular New Delhi, suffers from a temperature inversion at this time of year that traps air pollution
After being hit by the worst smog in years, New Delhi today saw thick fog following a couple of weeks of clear weather.
Thursday's fog affected in the Indian capital and nearby regions affected road, rail and air travel.
The visibility was below 50 metres (55 yards) early morning, leading to the Indira Gandhi International Airport suspending operations. Around four domestic flights were diverted in the morning.
"There was dense fog during the night which caused a lot of problems. It is natural and can lead to accidents on the road," said passenger Ravinder Singh, flying to Sydney via Bangkok, told Reuters.
Northern railways informed that 50 trains were running late.
The fog is expected to persist for a week, weather forecasters said.
North India, and in particular New Delhi, suffers from a temperature inversion at this time of year that traps air pollution.
The US Embassy's monitoring station recorded an air quality index (AQI) of 297 that is classified as "very unhealthy".
It, however, was not as bad as readings that approached 1,000, which is way off the AQI scale that runs to 500, during the first week of November, caused by firecrackers during the Diwali festival and burning of crop stubble in nearby regions.
(WION with inputs from Reuters)