The leader of Solomon Islands, who has developed close ties with China, on Friday joined Beijing in denouncing Japan's release of wastewater from the crippled Fukushima No. 1 nuclear power plant.

Addressing the United Nations General Assembly, Prime Minister Manasseh Sogavare said he was "appalled" at the move and warned of effects on his South Pacific archipelago.

"If this nuclear wastewater is safe, it should be stored in Japan. The fact that it's dumped into the ocean shows that it is not safe," he said.