The group sailed to the uninhabited islets, known as Senkaku in Japan and Diaoyu in China, aboard a fishing boat and stayed there for more than two hours, according to the Japan Coast Guard.
“The Coast Guard’s patrol vessels are always near the Senkaku islands. As their boat approached Senkaku, the coast guard verbally instructed them not to go any closer,” the spokesman said.
“We have told them that it was against the law to land on the island. They said they were going fishing. We are not in position to stop them from going to fishing.”
The four men returned to the boat before noon and began their return trip to Ishigaki.
The tiny isles have been a source of tension between the Asian giants for decades.
When Japanese Prime Minister Yoshihiko Noda visited China on December 25-26, he agreed with Beijing to set up a high-level meeting on maritime affairs in an effort to reduce tensions.