Twenty boats made the journey despite China anger, days after Japan deported pro-China activists from the archipelago.
Japan has rejected Chinese protests over the raising of a Japanese flag on disputed islands but also sounded a placatory note, saying ties with China are among the “most important” it has.
Japan stood firm in its insistence that islands where Japanese nationalists landed on Sunday, which it administers, were part of its territory, but said it wanted to improve ties with its neighbour.
“We have explained our nation’s basic position and told them that we cannot accept their claims,” Osamu Fujimura, Japan’s chief cabinet secretary, said in Tokyo on Monday.
“There is no doubt that the islands are our sovereign territory historically and under international law, and our nation controls the islands.”
Fujimura said China and Taiwan, which both claim the islands, had lodged objections after a group of Japanese nationalists landed on what Japan calls the Senkaku islands and China calls Diaoyu.
The flag-raising came just days after Tokyo deported pro-Beijing protesters who had landed on the same island.
Japanese authorities questioned on Monday the nationalists, including five local assembly members, who swam ashore on Uotsuri, the largest in a small archipelago.
The uninhabited islands, which are surrounded by rich fishing grounds, are controlled by Japan but also claimed by China and Taiwan.
The landing, which follows a similar visit by 14 Chinese activists detained and deported by Japan on Friday, has prompted nationalist outrage in China and is fuelling calls on both sides for aggressive government action that some fear could lead to an escalation of tensions.
Boats carrying Japanese nationals sail to disputed islands
Fujimura said Japanese authorities were handling the case “in accordance with domestic law” as the nationalists broke regulations banning landing on the islands.
“The Japan-China relationship is one of the most important bilateral ties for Japan,” he said.
Addressing journalists outside Yaeyama police station following Monday’s questioning, the nationalists said they did not expect to be charged by police.
“I believe it was an action that somebody needed to take. Going forward I hope the government and the parliament members will land [on the islands] and express to the world Japan’s wishes,” Yoshihiro Kojima, assemblyman of Ibaraki prefecture, said.
Yutaro Tanaka, assemblyman of Tokyo city’s Suginami district, suggested that the Japanese people “need to reconsider what the essence of peace is”.
“Nobody goes to war willingly,” he said. “However, if fire sparks are falling, we must sweep them off – as a human being, that kind of pride is essential.”
Eiji Kosaka, assemblyman of Tokyo city’s Arakawa district, called for defence forces to be placed on the islands “so that the nation would clearly show that our territorial islands on the border are being protected, and to speedily begin process for that”.
Protests across China
Protests against Japan broke out in more than a dozen Chinese cities including Beijing, as authorities allowed thousands of people to vent their anger over the territorial row.
Fujimura called on the Chinese government to ensure the safety of Japanese nationals in China as anti-Japan protests there have been targeting Japanese businesses, restaurants and cars.
The Japanese foreign ministry has separately issued a travel advisory, telling Japanese nationals to be on alert while staying in the country.
The latest anti-Japan protests are believed to be the most widespread in China since 2005, when several cities saw demonstrations over a slew of grievances including Japan’s wartime atrocities.
In the southern city of Shenzhen, which borders Hong Kong, protesters waved Chinese flags and shouted slogans as they marched on major streets, with the numbers swelling to about 1,000, the official Xinhua news agency said.