Japan joined the commercial space race Friday after its workhorse rocket put a paid-for South Korean satellite into orbit, pitting the country against Russia and Europe in the competition for customers.

But despite a degree of self-congratulation, space officials admitted they had to work hard to lower their prices if they were going to become truly competitive.

The H-IIA rocket took off from the southern island of Tanegashima on schedule at 1:39 am (1639 GMT Thursday), according to live images relayed by the Japan Aerospace Exploration Agency (JAXA).

The separation of South Korea's KOMPSAT-3 satellite from the rocket was confirmed around 16 minutes after take-off, followed shortly afterwards by the separation of three Japanese satellites that were also being carried.

"We were able to build a record of success for the first time. This gives us a springboard to win future contracts," said Hideaki Okuma, president of Mitsubishi Heavy Industries, which built the rocket.

The company, which has been operating the rocket since its 2007 privatisation, hopes to carry out more contract launches and secure a foothold in a potentially lucrative market currently dominated by Europe and Russia.

Science Minister Hirofumi Hirano said: "The success of the first commercial launch... is a reflection of steady technological advancement and improving reliability."

The launch Friday of the JAXA-developed rocket was its 20th success, set against one failure in 2003 when a rocket booster failed to separate after the launch and was destroyed.

The first foreign customer for H-IIA, the Korea Aerospace Research Institute (KARI), whose multi-purpose earth observation satellite was aboard, praised the Japanese technology.

"We are very happy with the launch by the H-IIA," KARI President Kim Seung-Jo told Japanese media in Tanegashima. "The credit for the success goes to the sophisticated capability of the H-IIA rocket."

The institute paid several billion yen (tens of millions of dollars), "the cheapest price in an international auction", the Sankei Shimbun reported, citing the institute. MHI declined to confirm the report.

But MHI President Omiya admitted that his firm needs to lower the launch cost to compete against foreign rivals.

"We are deepening our confidence in H-IIA. But the launch cost is higher than the international standard," he said. "We would like to make utmost effort to drive down the cost."

The rocket also put into space JAXA's Shizuku satellite, which will be used to monitor the circulation of water on Earth, officials said. The other two satellites were small experimental Japanese models.