TOKYO (AFP) - The Japanese government and Tokyo Electric Power (Tepco) were scrambling to reassure people on Friday that they have a lid on Fukushima after a senior utility executive said the nuclear plant was "not under control".

The remarks by Mr Kazuhiko Yamashita, who holds the executive-level title of "fellow" at Tokyo Electric Power, seem to flatly contradict assurances that Prime Minister Shinzo Abe gave Olympic chiefs a week earlier.

In a meeting with members of the opposition Democratic Party of Japan, Mr Yamashita was asked whether he agreed that "the situation is under control" as Mr Abe had declared at the International Olympic Committee meeting in Buenos Aires.

He said "I think the current situation is that it is not under control", according to major media, including national broadcaster NHK.

News of his comment prompted a rush by the government and Tepco to elaborate on the remark, saying he was talking specifically about the plant's waste water problem, and not the facility's situation in general.

Chief Cabinet Secretary Yoshihide Suga, Mr Abe's right-hand man, separately said Mr Yamashita was repeatedly pressed by DPJ lawmakers when he made the remark.

The view of Tepco as a company does not contradict Mr Abe's statement, Mr Suga added.

Tepco has poured thousands of tonnes of water on the Fukushima reactors to tame meltdowns sparked by the March 2011 earthquake and tsunami.

The utility says they are now stable but need to be kept cool to prevent them running out of control again.

Much of that now-contaminated water is being stored in temporary tanks at the plant, and Tepco has so far revealed no clear plan for it.

The problem has been worsened by leaks in some of those tanks that are believed to have seeped into groundwater, which runs out to sea.

The continuing nuclear catastrophe at Fukushima has come under the international spotlight in recent weeks as Tokyo fought off challenges from Madrid and Istanbul for the right to host the 2020 Games.