A group of Japanese researchers will conduct underwater surveys around two tiny islets at the center of a dispute with China.

Five researchers aboard the survey ship Koyo Maru will gather data on sea temperature and salinity levels from the Okinotorishima islets, about 1,730 km southwest of Tokyo, for several days starting Tuesday, according to National Fisheries University spokesman Masatake Kato.

Officials claimed the project was not politically motivated.

Tokyo reckons the uninhabited islets -- which Japan has fortified with extensive cement bulwarks to prevent them from eroding into a mere reef -- are full-fledged islands, which will allow Tokyo to lay exclusive claim to natural resources within a 200 nautical mile radius of the islets in the Pacific.

Beijing says the islets are too small to support such a claim.

Masanori Monde, who heads the Institute of Ocean Energy in Saga Prefecture, a cosponsor of the survey, said the Okinotorishima region was one of many areas the center was studying, denying any political motivations.

"This is a very preliminary survey, and it's too early to say whether we'll start any specific projects in the (Okinotorishima) area," he said.

The institute is developing technology to generate electrical power through differentials in sea temperature.

"This is a purely scientific project. We don't want to get involved with politics," Monde stressed.