Japan’s prime minister has acknowledged that Japanese nuclear plants need to increase anti-terrorism measures, a major weak spot found in the wake of the Fukushima disasters.

Prime Minister Shinzo Abe told a parliamentary session on Tuesday that investigation into the tsunami-hit Fukushima Dai-ichi nuclear plant revealed an overall lack of security. Abe says the government has instructed nuclear operators to upgrade security measures to match international standards. He says police have replaced private security guards to provide 24-hour watch around nuclear facilities.

Tokyo had repeatedly ignored US recommendations to strengthen severe accident measures at nuclear plants in case of a September 11-style attacks, saying the chances of such attacks on Japan were extremely low.

Regulators are currently working to beef up anti-terrorism measures at the plants.