Square-Enix has released a statement via PlayOnline revealing that the Final Fantasy XI server has been the victim of targeted attacks, resulting in service problems for hundreds of thousands of users.
"It has come to our attention that recent technical difficulties with our PlayOnline server are due to a DDoS from anonymous third parties. We have determined that this activity was undertaken with malicious intent," the statement said.
"Our technicians are taking every measure possible to prevent further attacks. However, attack methods have varied, which has caused a more time-consuming review of our network protection."
Square-Enix went on to reveal that it has been unable to determine the exact source of the attacks, but is working with ISP companies and law enforcement authorities in Japan, the US and Europe to hunt down those responsible.
"We deeply apologize for the inconvenience these attacks have caused in recent days and we regret that our investigation cannot allow for estimates as to when we expect service to return to optimal levels," the statement went on.
Although the problems have been occurring for some time now, Square-Enix said it could not announce the reasons behind them earlier "due to the unwanted effect it could have on our investigation, on the investigations of authorities abroad, and for stopping information that could be used to undertake additional network attacks."
But since difficulties have increased recently, the company said it felt it was time to disclose more information to users.
One theory as to the source of the attacks is that hackers in China have launched them as part of a political protest aimed at Japan.
Relations between the two countries are increasingly strained following the Japanese government's approval of new history textbooks for use in schools.
Chinese protesters say the textbooks gloss over Japanese atrocities committed before and during World War II - as an example, they describe the Nanjing massacre, in which between 50,000 and 300,000 Chinese civilians were killed, as "an incident". Demonstrations have been held in cities across China to protest.
The Japanese government says it should not be held accountable since the textbooks were published by private companies.
Square-Enix did not comment on the theory that the textbook row is linked to the attacks on its server.