BEIJING - China's meteorological authorities on Sunday asked the country's millions of holidaymakers to be alert to traffic accidents on their returning trips as fog has reduced visibility in some areas.

As of 5:00 am, the provinces of Hebei, Henan, Jiangsu, Hebei, Guizhou, Hunan were shrouded by fog, reducing visibility in some regions to less than 1 km, according to the National Meteorological Center (NMC).

The NMC said the fogs had already affected the country's high-speed roads, waterways and airlines.

Sunday was the last day of the eight-day holiday bridging the Mid-Autumn Festival and the National Day holiday. Due to a new policy that made most expressways toll free during the holiday period for passenger cars with fewer than seven seats, the country's expressways had seen increasing traffic flows during the period.

The NMC also forecast rains and temperature drops in the north due to a wave of cold front.