Websites of some Japanese government agencies were hit by cyberattacks over the weekend, temporarily blocking access to them, Kyodo news agency reported Monday, citing national police.
The attacks affected the websites of the National Personnel Authority, a video distribution service and a site run by the Cabinet Office, the National Police Agency said, according to Kyodo.
Police said they believed the websites were hit by distributed denial-of-service attacks in which hackers overwhelm a target website with massive amounts of data using a multitude of compromised "zombie" computers.
The NPA said online messages were posted in China calling for attacks on Japanese websites ahead of Sunday, the 80th anniversary of the "Mukden incident" which led to the Japanese invasion of China.
China has been accused of spearheading online attacks on government agencies and companies, allegations Beijing has always denied.
In June, Internet giant Google said a cyber-spying campaign originating in China had targeted Gmail accounts of senior US officials, military personnel, journalists and Chinese political activists.