Scientists at a South Korean experimental fusion reactor said Tuesday they had made a significant step forward in global efforts to produce clean and unlimited energy.

The KSTAR reactor generated a sustained super-hot plasma field during a demonstration in the central city of Daejeon, the ministry of education, science and technology said.

The ministry said KSTAR is one of the world's first research reactors to create plasma, which has been studied by scientists for the commercial use of fusion energy.

The reactor is a pilot device for the planned International Thermonuclear Experimental Reactor (ITER) in France, which is intended to be the world's first reactor emulating the sun's nuclear fusion principle to gain unlimited energy.

Fusion power is a technology involving the creation of an environment in which a super-hot plasma field can be maintained for long periods.

Once this state is reached, it can be fuelled by naturally abundant deuterium and tritium, two types of hydrogen, allowing a fusion reaction.

"Today's demonstration was highly successful," Kwon Eun-Hee, spokeswoman for the National Fusion Research Institute which operates the KSTAR reactor, told AFP.

The demonstration followed months of tests monitored by local experts and foreign scientists, she said.

KSTAR was built in September last year under a 309 billion won (306 million dollar) project related to the ITER project, which involves South Korea, the United States, Japan, the European Union, China and Russia.

South Korea has agreed to foot 9.09 percent of the 5.1 billion euro (8.1 billion dollar) cost of ITER by 2015, Kwon said.

South Korea, which has few natural energy sources, already uses conventional nuclear power stations to provide 40 percent of its power needs.