Japan's prime minister on Tuesday vowed to "expel by force" any Chinese landing on islands at the centre of a territorial row, after eight Chinese government vessels sailed into disputed waters.
"We would take decisive action against any attempt to enter territorial waters and to land" on the islands, Shinzo Abe told parliament in response to questions from lawmakers.
"It would be natural for us to expel by force if (the Chinese) were to make a landing.
Japan has earlier summoned the Chinese ambassador on Tuesday in protest over a flotilla of Chinese government ships that entered territorial waters near a disputed island chain.
Japan's foreign ministry said it had called in the envoy after eight Chinese vessels entered waters near the Senkaku islands, which China calls Diaoyu, the most in a single day since Tokyo nationalised part of the archipelago in September.
Eight Chinese government ships entered Japanese territorial waters near disputed islands Tuesday, the most in a single day since Tokyo nationalised part of the archipelago, the Japanese government said.
Japan's coastguard confirmed the vessels had entered waters near the East China Sea island chain, while the government's top spokesman said the flotilla was a one-day record since Tokyo's nationalisation in September.
The maritime surveillance ships entered the 12-nautical-mile zone off the Senkaku chain of islands, which China calls the Diaoyu, around 8:00 am (2300 GMT Monday), the Japan Coast Guard said in a statement.
State-owned Chinese ships have frequently spent time around the five disputed islands, also claimed by Taiwan, in recent months.
"It is extremely deplorable and unacceptable that Chinese government ships are repeatedly entering Japanese territorial waters. We have made a firm protest against China both in Beijing and Tokyo," Japan's Chief Cabinet Secretary Yoshihide Suga told reporters.
Meanwhile, a group of Japanese nationalists said it had sent nine ships to the area around the islands.