EDF's fleet of 58 reactors needs upgrades 'as quickly as possible' to be sufficiently robust in extreme situations, said France's nuclear safety regulator.

Stress tests at Finland's nuclear power plants show that no major modifications are needed, utilities Fortum and Teollisuuden Voima Oyj (TVO) have told the Finnish nuclear regulator.

European regulators have been publishing progress reports on the program of stress tests being carried out at nuclear power plants in response to the Fukushima accident.

CLARIFIED: Unit 3 at the Tomari nuclear power plant on Japan's northern Hokkaido island has resumed operation after a periodic inspection. It is the first reactor to be restarted in the country since the 11 March earthquake and tsunami.