Tokyo – More than 4,000 Indonesians will join a lawsuit against the Japanese government, demanding compensation for a dam funded by aid from Tokyo and which they say has destroyed their livelihood, supporters said on Wednesday.

The original suit, the first ever against a project funded by Japan's official development assistance (ODA), was filed last year in the Tokyo District Court by 3,861 Indonesians who said they were forcibly resettled to make way for the Kotopanjang Dam in Sumatra. Around 4,600 more people will join the suit on Friday, said Atsushi Saito, with a group supporting the plaintiffs.

Like the plaintiffs before them, they will demand five million yen ($41,650) each in compensation from the Japanese government and its foreign assistance body, the Japan International Cooperation Agency, for damage to their lifestyle, including a lack of fresh water and jobs in the area where they were resettled.

"There's no water where they live, it takes four hours a day to get water," Saito said. "Children can't go to school.

"The compensation is a secondary demand. What they really want is to return to the lives they had before, perhaps by dismantling the dam." A lawyer for the plaintiffs declined to comment, saying that details were still being worked out.

Also named in the original suit were the Japan Bank for International Cooperation (JBIC), a semi-governmental bank that provides loans to foreign countries and overseas projects, and Tokyo Electric Power Services Co, an affiliate of Tokyo Electric Power Co (TEPCO), Japan's largest utility.

The hydroelectric dam, completed in 1997, was built in Sumatra at a cost of some 31 billion yen. Plaintiffs say it has damaged the natural environment and that wild animals in the area, including elephants, face starvation, Kyodo news agency said. "The environmental damage has been huge," Saito said.

A Japanese Foreign Ministry official declined to comment on the suit.