The status of two Chinese government ships sent to assert Beijing’s claim over Japanese-controlled islands in the East China Sea remained a mystery early Wednesday, with no word from either government on the ships’ whereabouts.

China’s official news agency Xinhua reported that the two China Marine Surveillance ships “reached the waters around the disputed islands Tuesday morning. It said the Chinese agency in charge of the vessels had a plan to safeguard Chinese sovereignty and would “take actions pending the development of the situation. Since then, Chinese state media have been silent on the ships’ movements.

Japanese officials also had no comment on the status of the Chinese government ships. Japan’s coast guard has confronted Chinese fisherman and nationalists in the waters of the archipelago several times in recent years. It was not clear if Japanese authorities were taking similar action this time.

Japan refers to the disputed islands as Senkaku, while China calls them Diaoyu. The waters around the islands contain rich fishing grounds and potential oil reserves. Tokyo annexed the archipelago in 1895. Beijing claimed sovereignty over the islands in 1971 and called them part of Chinese territory since ancient times.

China said it sent the government ships to the archipelago in response to the Japanese government’s decision to buy some of the islands from a Japanese family that has owned them for decades. Japanese officials said Tuesday the $26 million deal was aimed at keeping the islands under “peaceful and stable maintenance.

The ultranationalist governor of Tokyo had been trying to buy the uninhabited islands since April with the aim of building structures on them. The Japanese central government has pledged to maintain the status quo.

Chinese defense ministry spokesman Geng Yansheng said Tuesday the military is “resolutely opposed to Japan’s nationalization of the islands. He said the Chinese military was “closely watching developments … and reserves the right to take corresponding measures.

Japanese news agency Jiji quoted “informed sources as saying the Chinese defense ministry’s statement suggests that “hardline anti-Japanese views are “increasing within the Chinese military.

Taiwan also claims the disputed islands. It sent a protest note to Japan about the purchase on Tuesday.

Tokyo Governor Shintaro Ishihara raised $18 million from private donations for his failed bid to buy the islands. Speaking Tuesday, he said the money will be kept in a fund until the central government agrees to his proposals to build docks and facilities for Japanese fishermen.