The number of confirmed coronavirus infections in Japan has topped the 1,000 mark, mostly from the Diamond Princess cruise liner, as the government reiterated that plans to host the Tokyo Olympics in July remained on track.

Five new infections were reported, in locations from Yamaguchi prefecture in the west to Hokkaido in the north, underlining the virus' spread across the country.

A total of 12 people have died, of which six were from the Diamond Princess, the health ministry said.