North Korean leader Kim Jong-un announced on Wednesday that his scientists have developed miniature nuclear warhead which can be mounted on ballistic missiles. State media published images of the leader standing next to what it claimed to be a miniaturised weapon.

However, it is impossible to ascertain the verity of the claim and there have been similar claims by Kim Jong-un which the experts have long expressed their doubts on. The North claimed to have been stepping up its aggressive rhetoric in response to some of the toughest sanctions adopted against it by the United Nations.

The Security Council passed sanctions against the state after it carried out a fourth nuclear test and launched a rocket, both of which violated the existing sanctions.

After the US and South Korea began their biggest ever war games, North Korea threatened both the nations with nuclear strikes, saying the rounds of military exercises were rehearsals for invading it.

The leader made the claim while he was inspecting the nuclear facility on Wednesday. “The nuclear warheads have been standardized to be fit for ballistic missiles by miniaturising them,” state media agency KCNA quoted him as saying. “This can be called true nuclear deterrent.”

The KCNA reported that Kim Jong-un also inspected warheads designed for thermo-nuclear reaction. The leader was greatly pleased with the achievement of his nuclear workers. If the claim is trues then the North can pose a serious threat to the South and to US.

The commander of US forces in South Korea, Gen. Curtis Scaparrotti, told reporters in October 2014 that North Korea keeps the capability of developing a miniaturised nuclear warhead, the BBC reported.

Skynews reported that a UN panel said it has “serious questions about the efficacy of the current UN sanctions regime” against the country, as the experts have pointed out that the country has been successful in evading its sanctions.