An activist who landed on the Diaoyu Islands is taken into police custody in Naha, the capital of Okinawa, on Thursday. [Photo/Agencies]

Any of Japan's unilateral moves against Chinese nationals is illegal and invalid, China's Foreign Ministry said Friday, after Japan decided to release 14 Chinese nationals it detained earlier this week.

Japanese Cabinet decided to release all 14 Chinese activists who were arrested on Wednesday after seven of them landed on one of the Diaoyu Islands in East China Sea, Osamu Fujimura, top government spokesman, told a press conference on Friday.

All 14 Chinese nationals have arrived at Naha Port, Okinawa, and been transferred to immigration authorities as of Friday morning, said Okinawa police.

They may be released Friday afternoon, possibly by plane or boat, according to local media reports. Further plans were being discussed, according to media.

The 14 Chinese activists, despite obstruction by Japan Coast Guard patrol ships, arrived at Diaoyu Islands by a Hong Kong fishing vessel on Wednesday to assert China's territorial claim to the islands.

China on Wednesday lodged solemn representations with Japan on the latter's illegal detention of Chinese nationals on the Diaoyu Islands.