Japan's health ministry says the influenza season has begun across the country.

The ministry has been receiving reports on the number of flu patients from around 5,000 medical institutions nationwide.

It said on Friday that 5,127 people were diagnosed with the flu in the week through Sunday at these institutions, which was up 829 from the previous week.

The average number per institution was 1.04. A figure above 1 indicates the onset of the flu season.

This is the second earliest time for the flu season following 2009 after record keeping began with the current method. The statistics does not include last year, when a flu epidemic continued throughout the year.

By prefecture, the average stood at 10.64 in Okinawa, 2.09 in Shizuoka, 2 in Chiba, 1.66 in Oita and 1.62 in Fukui. The number of flu patients rose in 32 prefectures week-on-week.

Health ministry officials are urging people to take basic anti-infection measures, such as washing hands and wearing a mask, as well as considering getting vaccinated.