The National Police Agency said on Friday that more than 90 per cent of cyber attacks on its website carried out overnight on July 10 originated from Internet Protocol addresses in China. The findings came after the NPA determined that similar attacks on its website last September were mostly attributable to Chinese IP addresses.

Access to the NPA website was temporarily interrupted on the night of July 10 through the early hours of the following day as the apparent number of users accessing the website surged to about 20 times the normal level, the NPA said, adding that no data was breached.

Through the International Criminal Police Organization, or Interpol, the NPA asked the Chinese side to determine those involved in the act, it said.

The NPA said there was writing on an Internet message board in China calling for attacks on the NPA website. The message referred to an incident in which Japanese Air Self-Defense Force fighter jets scrambled in response to the flight of a Chinese reconnaissance plane near the disputed Senkaku Islands, it said.

The message board also had posts calling for the websites of Japan's Defense Ministry and Finance Ministry to also be targeted. The Finance Ministry website came under attack on the night of July 12, with some interruption to viewing of the site.