Japanese government officials on Wednesday told diplomats they were still considering options for handling contaminated water at Tokyo Electric Power's wrecked Fukushima nuclear power plant amid worries the water may be dumped into the ocean.

A massive body of tainted water - more than 1 million tons as of August - is building up at the plant, crippled by a 2011 earthquake and tsunami, as operator Tokyo Electric (Tepco) tries to cool the melted fuel cores by pouring water over them. Tepco has said it will run out of tank space by mid-2022.

The briefing for embassy officials in Tokyo follows a meeting in August of a government panel of experts looking into ways to solve the water problem. The final government decision will be made based on a report by the panel.

Asked by one of the participating embassy officials about the timing of the panel decision, Japanese officials said such timing has not been fixed, according to a media briefing held later on the day.

The briefing for diplomats was attended by 27 embassy officials from 22 countries and regions, including South Korea and the US. No protests or demands have been made by the participating diplomats, according to the media briefing.

"With transparency in mind, Japan will continue providing the international community with information (on the Fukushima situation)," Koichiro Matsumoto, the Japanese Foreign Ministry's director of international cooperation, told diplomats at the start of the meeting, the outset of which was open to media.

The meeting comes after South Korea, locked in a trade and territorial rows with Japan, last month summoned a senior official from the Japanese Embassy in Seoul, to ask about Japan's stance on dealing with the Fukushima water.

But a Japanese Foreign Ministry official told reporters that briefings for diplomats on the matter have been held more than 100 times since the March 2011 disaster, and the one on Wednesday was held to pass information discussed at the latest government panel meeting in August.