Prime Minister Manmohan Singh on Saturday left for a four-day visit to South Korea where he is expected to unveil steps conceived by India to tackle challenges of nuclear terrorism before 57 world leaders at the Nuclear Security Summit in Seoul.

Singh said he would also underline India's continuing support to a world free from nuclear weapons. The aim of the summit is to focus attention of countries with considerable nuclear capabilities on the threat posed by nuclear terrorism.

"This remains a continuing concern," Singh said in a pre-departure statement. The Summit is expected to be attended by 45 heads of state or governments including US President Barack Obama, Russian President Dmitry Medvedev and Chinese President Hu Jintao.

Pakistan Prime Minister Yousuf Raza Gilani is also travelling to Seoul and reports from Islamabad said he was likely to meet Singh on the sidelines of Summit.

Leaders of Australia, Japan, Indonesia, France, the UN and the EU, will also be at the Summit alongwith Deputy Prime Ministers or Foreign Ministers of 13 countries.

Pointing out that India is expanding its nuclear power programme to diversify its energy mix and enhance energy security, Singh said that in order to retain public support for harnessing the benefits of nuclear energy, "we must be able to assure them of the highest levels of nuclear security and safety."

This, he said, is 'even more important' after the Fukushima accident in Japan last year. "India has prepared a national report which will be shared during the Summit," the Prime Minister said adding he would highlight the high priority India attaches to nuclear security, safety and non-proliferation and its impeccable record in this regard.

Singh said he expected the Seoul Summit to review actions that countries have taken to strengthen nuclear security since the last meet and recommend further steps to enhance the global nuclear security architecture.

"The main objective of the Summit has been high-level attention on the global threat posed by nuclear terrorism and the measures that are required to prevent terrorists and other non-state actors from gaining access to sensitive nuclear material and technologies," Foreign Secretary Ranjan Mathai had said.

During his visit to Seoul, Singh is scheduled to hold talks with South Korean President Lee Myung-bak and leaders of some other countries. An agreement on simplifying issuance of visas between India and South Korea would be signed after talks between Singh and Lee.

"I look forward to my bilateral meeting with President Lee to undertake a comprehensive review of our relations with the Republic of Korea, and identify new steps for the future," the Prime Minister said in the statement.

Describing South Korea as a strategic partner and an important pillar of India's 'Look East' policy, he noted the two countries have a vibrant trade and investment relationship and partnership in science and technology, education and energy holds enormous promise.

Singh would also seek to strengthen people-to-people contacts between the two countries, strengthen cooperation in the field of science and technology, and also coordinate the thinking on matters relating to regional security and international events.