South Korea Wednesday showed off high-tech bomb-disposal robots and anti-terrorism drills by special police commandos to ensure that a nuclear summit passes off safely next month.

Police said some 40,000 officers would be deployed during the Nuclear Security Summit in Seoul to guard against potential attacks by North Korea or terrorists.

Top leaders from some 50 nations and four international bodies will attend the March 26-27 summit to discuss issues including how to restore confidence in the nuclear industry, organisers said.

"We can't rule out the possibility of provocations by the North given its political situation," national police chief Cho Hyun-Oh said during an event to showcase preparations for the event.

He cited the North's alleged torpedo attack on a South Korean warship that claimed 46 lives in March 2010 and the shelling of a border island that killed four South Koreans in November of the same year.

Commandos dressed in combat gear demonstrated how to deal with rowdy protesters or terrorists in a hostage situation, as well as how to detect and remove bombs using sniffer dogs and robots.

"We will boldly enforce the law when deemed necessary," Cho said.

South Korea has repeatedly voiced concern over potential attacks by the North ahead of major global events such as the G20 summit in Seoul in 2010, though such predictions have not come into reality in recent years.

A North Korean agent bombed a South Korean airliner in 1987 in the run-up to the Olympics in Seoul, and a bloody naval clash erupted in 2002 when South Korea co-hosted the World Cup.

The nuclear summit is the second since US President Barack Obama inaugurated the forum in Washington in 2010 as a way to strengthen international safeguards and prevent nuclear terrorism.

Report: China agrees to invest $3 bln in N. Korea zone
Seoul (AFP) Feb 15, 2012 - China has agreed to invest about $3 billion in developing North Korea's northeastern free trade zone as an export base, a report said Wednesday.

The deal was probably reached before or just after the North's long-time leader Kim Jong-Il died on December 17 of a heart attack, South Korea's Yonhap news agency said.

China will build an airport, a power plant, a cross-border railway and piers in the North's Rason economic zone bordering China and Russia by 2020, it said.

In return China has secured the right to use the Rason port for 50 years, the agency said, citing sources in Seoul and Beijing.

The port -- formerly known as Rajin and Sonbong -- would give China's northeastern provinces direct access to the Sea of Japan.

Impoverished communist North Korea is striving to revitalise its economy through foreign investment in Rason, which was declared a special economic zone in 1991 but failed to flourish.

China, Pyongyang's sole major ally and biggest trade partner, is actively exploring investment opportunities in North Korea as South Korea's economic influence dwindles amid political tensions.

The North's dependence on Beijing grew as international sanctions over its missile and nuclear programmes restricted access to international credit.

Last June the two countries broke ground for a joint economic zone near the North's west coast, on an island in the estuary of the Yalu border river.