According to the agency, citing multiple sources, the protest was issued by the Japanese Foreign Ministry to the Chinese Embassy by phone as well as via the Japanese Embassy in China.
On 8 May, four Chinese patrol ships one by one entered the Japanese territorial waters, with two of them trying to pursue a fishing vessel there. A similar incident took place earlier in the day when four patrol ships emerged near the border, with two of them crossing into the Japanese territory.
Following World War II, the islands were controlled by the United States and handed over to Japan in 1972. Both Taiwan and mainland China claim that Japan has been illegally seizing them while Tokyo rebuts that they have begun claiming the islands for themselves after in the 1970s the surrounding water area was found to be full of valuable minerals.
The tensions have exacerbated after the Japanese government bought three of the islands from a private owner in 2012.