A thick blanket of low cloud descended on Melbourne this morning causing delays for commuters on land and in the air. Visibility is substantially reduced, in some cases to 200 metres. The Bureau of Meteorology says the fog will linger for some time.

BOM has issued a road weather alert for all Melbourne suburbs. Drivers are being told to expect delays going into the city.

The State Emergency Service has advised people to reduce speed, use headlights and maintain a greater distance between theirs and the vehicle in front of them.

Delays of around 15 minutes are being experienced across Melbourne roads. Radio station SEN reported several crashes had occurred due to poor visibility.

Melbourne is currently experiencing delays of up to an hour on both inbound and outbound flights. A spokesperson for the airport has advised all passengers call their airlines for detailed updates on delays.