China has apologised for what it called an accidental incursion by one of its submarines into Japanese waters last week, Tokyo has said.
The incident sparked a two-day chase by Japan's navy
Japan's Foreign Minister Nobutaka Machimura said China had expressed regret for the incident, which sparked Japan's first naval alert since 1999.
Japan lodged a protest last Friday after saying the sub, which entered waters off Okinawa, was Chinese.
Beijing has not yet publicly confirmed its reported apology.
Japanese officials said they had been told that the Chinese submarine entered Japanese territorial waters by mistake.
Japan's top government spokesman, Hiroyuki Hosoda, said that Chinese Vice-Foreign Minister, Wu Dawei, told the Japanese ambassador to China on Tuesday morning that the sub was on routine manoeuvres, and that Beijing regretted the incident.
"We consider this to be an apology," Mr Hosoda told a news conference.
Japanese Foreign Minister Mr Machimura said the sub had made the incursion due to a "technical error".
"The Chinese side said there is no change in its stance that it intends to build partnership with neighbour Japan," Mr Machimura added.
The incident threatened to further strain relations between Japan and China, already locked in disputes about contested resources, and sensitivities over their recent history.
The submarine was first spotted last Wednesday near the Sakishima islands, which lie about 120km (75 miles) south of the disputed Senkaku islands - known as the Diaoyu in Chinese.
It sparked a two-day chase, with Japan concluding it was Chinese due to its noise and general direction as it fled.