TOKYO (Reuters) - Japan said on Saturday it will take the long-running islands territorial dispute with South Korea to the International Court of Justice, after South Korean President Lee Myung-bak made a surprise visit to the islands this week.

The islands, known as Takeshima in Japan and Dokdo in South Korea, lie equidistant from the two mainlands and are believed to contain frozen natural gas deposits potentially worth billions of dollars.

Lee became the first South Korean leader on Friday to make the trip to the islands, which have been a persistent irritant in relations between the two countries.

"Japan decided to act to peacefully solve the issue by bringing it to International Court of Justice," a spokesperson for Japan's Foreign Minister Koichiro Gemba said via an e-mailed statement on Saturday.

"Having seen Republic of Korea take such an unacceptable action, we believe that letting Japan's case on Takeshima known to the world, through ICJ, is more important than holding back, giving consideration for the whole Japan-ROK relations."

The timing and content of the case will need to be worked out, but action will be taken in the "not so distant a future", he said.

Japan recalled its ambassador to South Korea on Friday after Lee visited disputed islands.

Officials in South Korea said the visit was meant to highlight the islands' importance as a natural reserve and was not aimed at stirring up trouble.

Lee travelled to a larger island called Ulleungdo off the Korean peninsula's east coast, which is not disputed, and made the final leg under tight security with military and coast guard escort.

(Reporting by Junko Fujita; Editing by Michael Perry)