Japan’s Prime Minister Shinzo Abe has ordered his defence minister to strengthen surveillance around islands at the heart of a territorial feud with China.
Earlier, the Deputy Foreign Minister summoned the Chinese ambassador to protest against what he called an incursion by four Chinese maritime surveillance ships near the islands.
The ambassador responded by re-iterating his country’s claim over the islands, known as Diaoyu in China.
Kyodo news agency quotes Prime Minister Abe as saying he wants to respond firmly.
Mr Abe, whose conservative Liberal Democratic Party returned to power last month, has vowed a tougher stance in the territorial feud.
China’s State Oceanic Administration confirmed four Chinese marine surveillance ships were patrolling waters near the islands.
The ships entered the area around noon on Monday and left in the early hours of Tuesday.
“Japan has continued to ignore our warnings that their vessels and aircraft have infringed our sovereignty,” the Communist Party chief of China’s marine surveillance corps, Sun Shuxian, said in an interview posted on the Oceanic Administration’s website.
“This behaviour may result in the further escalation of the situation at sea and has prompted China to pay great attention and vigilance,” Sun was quoted as saying.
Sino-Japanese ties chilled after the Japanese government bought the disputed islands, known as the Senkaku in Japan and Diaoyu in China, from a private Japanese owner last September.