SEOUL (AFP) - South Korea has completed a major naval base on the southern resort island of Jeju, the navy said on Thursday (Feb 25), a project that sparked fierce protests by residents and activists.

The US$806 million (S$1.1 billion) base, completed after six years of construction, will provide the navy with a deep sea port in the south.

South Korea is surrounded by sea on three sides - the west, east and south - and the base will grant its navy quick access to the eastern and southern parts of the East China Sea for the protection of the country's trade routes, naval authorities said.

It will also serve as home for quick strike forces that can be dispatched against enemies who could bypass frontline navy forces deployed in the western and eastern sea to invade the country.

With its pier and breakwater measuring 2.4km and 2.5km in length, the base can simultaneously dock 20 combat vessels and two cruise ships of the largest class.

It will double as a cruise ship port when a separate civilian pier is completed next year.

The navy plans to host an opening ceremony on Friday (Feb 26), with a naval parade by the country's most sophisticated warships.

The government first launched the Jeju base construction project in 1993 as part of efforts to consolidate South Korea's maritime sovereignty.

Ground was broken six years ago, but the construction work was once put on hold in the face of intense protests by residents, environmentalist and pacifists.

More than 600 protesters have been arrested. Many of them were indicted and fined.