North Korean leader Kim Jong Un has urged his country's officials to boost production of nuclear material for military purposes, state media reported Tuesday, as Pyongyang unveiled a new, apparently smaller, tactical nuclear warhead.

Kim appeared in scenes broadcast by state media, surrounded by military generals, as he inspected a number of green warheads and a smaller size called "Hwasan-31", meaning volcano in Korean.

France condemned what it described as "North Korean provocations," and French Foreign Ministry spokeswoman Claire Legendre said Tuesday that she "takes note, with deep concern, of the renewed North Korean leader's call to accelerate North Korea's production of nuclear weapons," urging the country "to comply with its international obligations... .and immediately put an end to its destabilizing actions.”

North Korea has often sought technology that would enable it to "miniaturize" a warhead that could be mounted on an intercontinental ballistic missile to threaten the United States. Graffiti on the walls suggests this may be the case with Hwasan-31.
Kim listened to a briefing from officials at the Nuclear Weapons Institute, according to the official North Korean Central News Agency.

He called on the officials to "expand in a far-sighted way the production of nuclear materials intended for making weapons for the comprehensive implementation of the plan (...) to increase the nuclear arsenal exponentially."

Kim added, according to the agency's report, that when North Korea manufactures its nuclear weapons "without defects", "the enemy will fear us and will not dare to provoke the sovereignty of our country, our system and our people."

Experts said that the disclosure of a possible tactical nuclear weapon, carries indications of technical development and could hint at an imminent nuclear test.

Kim's remarks come ahead of the arrival of a group of US warships in South Korea on Tuesday.

And relations between the two Koreas are at their lowest levels in years, with Seoul and Washington promoting joint military exercises, while North Korea is conducting provocative weapons tests, and the South is responsible for the deteriorating security situation.

"The current hard-line approach is likely intended to justify their testing of new weapons and nuclear testing in the future," said Cheong Seong-chang, a researcher at the Sejong Institute.

And he believed that "North Korea revealed a clearly miniature tactical warhead this time."

"The possibilities of North Korea carrying out a seventh nuclear test with these tactical nuclear warheads as a next step have increased," he told AFP.

Pyongyang is conducting missile tests, which are a "response" to the US-South Korean military exercises. This represents a large and unsustainable financial burden on the poor country, according to one expert.

"North Korea has warned of a massive retaliation against every joint exercise of South Korea and the United States, but given the number of missiles fired, they can't go on forever," the professor at Ewha University, Seoul, told AFP.

"In that case, the seventh nuclear test will be an end of sorts. They will declare themselves a nuclear power and return to the negotiating table with the United States," he added.

North Korea's military on Monday conducted exercises simulating a nuclear attack using tactical ballistic missiles, according to a separate report by the official North Korean news agency, as part of an unprecedented number of tests since the beginning of the year.

"North Korea is sending a very coherent message. They are fighting for recognition as a pure nuclear power," Park said.

North Korea also seeks to diversify production of means capable of carrying its nuclear warheads, in addition to increasing its nuclear stockpiles.

On Tuesday, it said it had conducted a second successful test of a guided nuclear torpedo capable of pursuing underwater targets.

Last week, the first test of this new weapon, which bears the name "Haile", or "tsunami" in Korean, was announced, in response to the recent military exercises between the United States and South Korea, the largest in five years.
Seoul questioned those statements, and its military said it was "considering the possibility" that the experiment was exaggerated and even "fabricated".

There have been indications that "North Korea has developed unmanned submarines, but it is likely that they are still in the early stages," according to the Joint Chiefs of Staff.
Pyongyang said Tuesday that the torpedo "Hebble" maneuvered underwater "for 41 hours and 27 minutes, following a simulated course of 600 km" before exploding with a target off North Hamgyong Province early Monday, according to the official KCNA news agency.
The agency said that the experiment "proved all the strategic characteristics of the weapon system, in addition to its safety and solidity."
Reports indicated that Russia has developed a similar weapon, the "Poseidon" guided nuclear torpedo, but the complex technology required for such weapons may exceed North Korea's capabilities, according to experts.