Popular Japanese video-sharing website Niconico has suspended its services as it has been under "a large-scale cyberattack," its operator said.

"Currently, Niconico is under a large-scale cyberattack, and we are suspending our services to minimise its impact," operator Dwango said in a statement late Saturday.

"We are hastily investigating and taking countermeasures, but we won't be able to restore the service until we make sure about its safety after completely excluding the impact of the cyberattack," it said, adding it didn't expect to be able to restore the service this weekend.

Niconico is one of the largest video-sharing services in Japan where users share various videos ranging from music to sports to a range of hobbies, while live streaming of programmes including press conferences by government officials is also available.

In addition to Niconico, its parent company Kadokawa's official website and its e-commerce site "ebten" were also affected by a possible "unauthorised access from outside," the publisher said Sunday.

"We offer our deep apology for causing worries and troubles over the phenomenon that several websites of Kadokawa group have been unavailable since before dawn of Saturday," Tokyo-based publisher Kadokawa said.

Kadokawa was investigating the impact from the attack, including "whether there have been leaks of information or not," and was also cooperating with external experts and police, it said.

Dwango said it would give an update on Monday.