North Korea's threat of underwater nuclear attacks, which are difficult to detect beforehand, is looming large.

The North disclosed through state media Friday that it launched its first “tactical nuclear attack submarine” that can fire nuclear missiles underwater.

Photos North Korea disclosed reveal 10 vertical launch tubes for short and medium-range ballistic missiles.

The submarine is presumed to be capable of firing not only ballistic missiles tipped with nuclear warheads but also "Haeil" torpedoes. The North unveiled what it claims to be nuclear-capable torpedoes, dubbed "Haeil," at a parade in late July. The torpedo or "underwater nuclear attack drone" can penetrate coastal defenses and create "a super-scale radioactive tsunami through an underwater explosion."

Experts say the latest submarine appears to be based on the old Romeo-class submarine, and the launch tubes seem to be installed when the old sub was remodeled. The vessel appears coarse. South Korea's Joint Chiefs of Staff assessed that the submarine does not seem to be capable of being fully operational.

However, the problem is that even if it is decrepit, firing a nuclear missile just once could be threatening enough.

North Korean leader Kim Jong-un called on the country to convert all of its medium-sized subs into nuclear-capable versions.

If the North fires submarine-based ballistic missiles from its fleet of about 20 remodeled submarines all at once, it would be nearly impossible to intercept them with current US-Korea defense systems.

The submarine, if loaded with a nuclear torpedo, can threaten an aircraft carrier. In 2010, a torpedo fired by a North Korean submarine blew up a South Korean naval warship, killing 46 seamen.

Kim is committed to building a nuclear-powered submarine. To build a nuclear-powered submarine, the North needs technology to make a small reactor and design a nuclear sub. But Seoul must take seriously the possibility of Russia offering related technical advice to Pyongyang.

If North Korea owns a nuclear-powered submarine that can launch ballistic missiles tipped with nuclear warheads, its threat to regional security will go beyond imagination. It has already secured solid-fuel intercontinental ballistic missiles that can strike the continental US. Its tactical nuclear weapons can devastate the entire area of South Korea and US bases in Japan. Compared with these land-based missiles, nuclear-powered submarines that can operate secretly underwater for a long time are excellent means for stealth attacks.

It is urgent to draw up emergency response procedures.

South Korea, the United States and Japan must build up their joint ability to monitor and sink North Korean subs. The US needs to station a strategic nuclear-powered submarine near South Korea.

Nuclear weapons are best deterred only with nuclear weapons. Similarly, nuclear-powered subs can be deterred by nuclear-powered subs.

South Korea has submarine-based ballistic missiles deployed, but obviously they have limits when compared with North Korean subs that can fire nuclear warheads.

The South Korean military has pursued the possession of a nuclear-powered submarine but its efforts to secure nuclear submarine fuel have been frustrated by the agreement between the two countries concerning peaceful uses of nuclear energy.

In March, Washington allowed the sale of US-manufactured, nuclear-powered attack submarines to Australia amid growing concerns about China's influence in the Indo-Pacific region.

South Korea needs them as much as Australia to respond to North Korea's nuclear threat to the world. Nuclear-powered submarines are not necessarily related to nuclear bombs. North Korea will certainly keep trying to get nuclear-powered submarines that can launch nuclear warheads. Washington needs to consider allowing South Korea's possession of nuclear-powered submarines.

South Korean military authorities and security experts rate the threat from the latest North Korean submarine as low, but Seoul cannot let down its guard. The latest North Korean submarine may appear rough but its existence itself can cause a butterfly effect on the landscape of Northeast Asian security.