North Korean leader Kim Jong Un
North Korean leader Kim Jong Un provides field guidance at the Sinpho Pelagic Fishery Complex, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on May 9, 2015. Reuters/KCNA

Responding to North Korea's recent underwater ballistic missile tests, South Korea said Monday that it will retaliate "mercilessly." South Korean Defense Minister Han Min-koo made the statement at an emergency meeting between the government and the ruling Saenuri Party to discuss the recent provocations by Pyongyang.

"(South Korea) will completely sever the chain of provocations by mercilessly dealing with any provocations," Han said at the security meeting, according to Yonhap, adding: "Retribution for provocations is an order from the people."

"Our military will stand with solid military readiness and make flat-out efforts for citizens to lead their everyday lives at ease," he said.

North Korea had said on Saturday that it has successfully tested a newly developed strategic ballistic missile from a submarine, calling it a “world-level strategic weapon.” The date of the missile's testing was not revealed, but the announcement of its success came a day after the North’s military threatened “targeted strikes” against the South Korean navy for allegedly violating territorial waters off the western sea border.

The missile is “capable of striking and wiping out in any waters the hostile forces infringing upon the sovereignty and dignity of” North Korea, KCNA, the country’s official news agency, said Saturday.

"We urge North Korea to immediately stop developing SLBMs (submarine-launched ballistic missiles), which hinder the stability of the Korean peninsula and Northeast Asia," Kim Min-seok, spokesman for South Korea's defense ministry, told reporters on Monday, according to Reuters, adding that North Korea still needed time to make its submarine-launched missile system fully operational. Another South Korean defense official told Reuters, that within three years, the North could develop a fully operational submarine with ballistic missiles.

The latest missile launch is widely seen as a threat to the North's neighbors such as South Korea, and also the United States, which is conducting military drills with Seoul.

Pyongyang's missile launch comes despite a United Nations' ban on North Korea developing or using ballistic missile technology. North Korea, which also boasts about the launch of a functional communications satellite, is, however, suspected to be working on a missile-launch capability for its submarines. In December 2012, North Korea also reportedly launched a long-range rocket and put an object into orbit, rebelling against warnings from international groups.