Warnings of a further possible nuclear catastrophe in Japan by Europe's energy chief were based on media reports and his personal fears, his spokeswoman said after the comments alarmed financial markets.

EU Energy Commissioner Guenther Oettinger earlier warned of "further catastrophic events" in the coming hours in Japan, saying they "could pose a threat to the lives of people on the island."

But his spokeswoman, Marlene Holzner, later clarified the situation.

"He just wanted to share his concern and that he was really touched by all the images of people and the victims...and in this sense, he said that according to we have seen in the media it seems that in the nuclear power plants at the moment we do not have technical control," Holzner told Reuters Insider TV. "He referred to media reports that say that we could imagine there is a partial meltdown."

Britain's FTSE 100 share index fell after Oettinger said the situation in Japan was out of control and U.S. markets also declined, with the Dow Jones industrial average last standing down 0.9%.