This image, provided by the Defense Acquisition Program Administration, shows a virtual image of the third Changbogo-III Batch-II class submarine, Oct. 30. Yonhap

South Korea has cut steel for its third and last 3,600-ton-class naval submarine, the state arms procurement agency said Wednesday, amid efforts to bolster underwater defense capabilities against North Korean threats.

The steel-cutting ceremony for the final series of three Changbogo-III Batch-II class submarines took place at shipbuilder Hanwha Ocean's dockyard in Geoje, 331 kilometers southeast of Seoul, according to the Defense Acquisition Program Administration (DAPA).

The 89-meter-long Batch-II submarine is part of the military's Changbogo-III or KSS-III program to acquire advanced diesel-electric attack submarines.

The Batch-II model is expected to have 10 vertical launch tubes for submarine-launched ballistic missiles (SLBMs), up from six equipped in the 3,000-ton Batch-I submarines.

The new submarine's SLBM system is expected to serve a key role for the military's Kill Chain preemptive strike platform designed to eliminate key North Korean nuclear and missile targets if there are clear signs of intended use.

The new submarine is expected to be completed by 2029 and delivered to the Navy in 2031 following trial operations.

All three of the Batch-II submarines are currently under construction, with the first of the three submarines scheduled to be delivered to the Navy in 2027. (Yonhap)