Prime minister Manmohan Singh on Wednesday assured the Lok Sabha that nuclear facilities in the country were "world-class" and all efforts were being made to maintain the best safety standards for both on-shore and off-shore nuclear power plants.

"Safety concerns are paramount...You have my assurance that while expanding our nuclear facilities we will not compromise on nuclear safety. This is an on-going process. Our nuclear facilities are world-class," Singh, who also holds the Atomic Energy portfolio, told the Lok Sabha during Question Hour.

He said that after the recent tragedy in Fukushima, Japan where a nuclear power plant was hit during a Tsunami, he had ordered nuclear agencies like NPCIL, BARC and AERB to re-look into the issue of safety of India's nuclear installations.

The prime minister's remarks came in response to a query from Jaswant Singh (BJP) about the steps being taken for ensuring safety of the nuclear power plants in Rajasthan.

The BJP leader said six nuclear plants were already active in Rawatbhatta in Rajasthan and the seventh plant was coming up. He insisted that the Fukushima tragedy was a lesson and consequences of such disasters are phenomenal.

Earlier, in reply to a question, minister of state in PMO V Narayanasamy said that the prime minister has asked AERB to review the safety measures and has held meetings with the departments concerned and authorities to discuss the issue.

"Four committees have been formed to go into additional security measures after the Fukushima tragedy. AERB has constituted a committee," Narayanasamy said.