A ceremony for the ship baptised the Kang Kon -- after a top North Korean general killed in the 1950-53 war -- was held on Thursday at the Rajin shipyard, up the coast from where the failed attempt occurred, according to Pyongyang's official Korean Central News Agency.

"Just over two weeks since the accident, the ship was safely raised and floated, and today, as planned, complete restoration has been finished," Kim said, according to KCNA.

Kim has also approved a plan to build two more destroyer-class vessels next year, the agency added.

The decision "heralds a significant and dramatic change in the status and defence activities of (our) Navy," Kim said, according to KCNA.

Photos released by the agency showed Kim, wearing a large straw hat and beaming happily, accompanied by his daughter Ju Ae, considered by many experts to be his likely successor.

He claimed that the "provocative intentions of the US and its allies" have recently become "more blatant, and the level of threats to our security has clearly gone far beyond the dangerous limit".

"We must develop our naval power more comprehensively and rapidly so that the enemy cannot even think of carrying out aggressive actions in the waters around us," the North Korean leader said.

The successful launch comes after Pyongyang last month announced "a serious accident" when workers first tried to put the 5,000-ton destroyer into water in the northeastern port city of Chongjin.

The mishap crushed sections of the bottom of the newly built ship. Pyongyang later covered it with a tarpaulin, satellite images showed.

South Korean intelligence believe North Korea's so-called "side-launch attempt" of the ship failed, and the vessel was left listing in the water.

Kim called the incident a "criminal act caused by absolute carelessness" and state media subsequently reported the arrest of four officials in connection with the botched launch.

But the country said soon afterwards that the extent of damage to the vessel was "not serious", and that it would take "two or three days" to drain it, and another 10 to restore the destroyer's side.

The South Korean military estimated that, based on its size and scale, the new warship was similarly equipped to the 5,000-ton destroyer-class vessel Choe Hyon, which North Korea unveiled in late April.

Seoul's unification ministry, which manages relations with Pyongyang, said no "external structural defects have been identified on the destroyer".

But "continuous monitoring is required to determine whether it is functioning normally," the ministry said in a statement.

- Russian help? -

Pyongyang has said the Choe Hyon is equipped with the "most powerful weapons," and that it would "enter into operation early next year."

Some analysts said the ship could be equipped with short-range tactical missiles capable of carrying nuclear warheads -- although North Korea has not proven it has the ability to miniaturise its atomic arsenal.

Seoul's military has said the Choe Hyon could have been developed with Russian help, possibly in exchange for Pyongyang deploying thousands of troops to help Moscow fight in Ukraine.

North Korea confirmed in April for the first time that it had deployed troops to Russia to support Moscow in the Ukraine war.

Hong Sung-pyo, a senior researcher at the Korea Institute for Military Affairs, said it is "almost certain" that the North's latest warships are a result of Russia's assistance.

"North Korea is one of the very few countries that have supported Russia's war in Ukraine. Since it has provided very tangible assistance - including weapons and even personnel -- Russia will find it difficult not to reciprocate," he told AFP.

"What Pyongyang currently seeks the most are hard currency and advanced military technology."

South Korea's new president, Lee Jae-myung, elected last week in a snap election, has promised a more dovish approach towards Pyongyang, compared with that of his hawkish impeached predecessor Yoon Suk Yeol.

The Lee administration has halted loudspeaker propaganda broadcasts along the border, which Seoul began last year following a barrage of trash-filled balloons flown southward by Pyongyang.

North Korea had resumed its own propaganda broadcasts, sending strange and eerie noises into the South, but it appears to have stopped.