North Korea's chemical warfare capabilities

We tend to focus on North Korea's nuclear threat and its visible, increasingly successful missile tests, but Kim Jong-Un also possesses one of the world's largest stockpiles of chemical weapons.

The country's chemical arsenal ranks third, behind the US and Russia, according to the Nuclear Threat Initiative project.

Its most recent report put North Korea's estimated chemical weapons stores at 2,500 - some 5,000 tons.

:: 'Weapon of mass destruction' killed Kim

Pyongyang denies it has any such weapons, but research sponsored by the South Korean government says it has four military bases equipped with chemical weapons, 11 facilities to produce and store them, and 13 dedicated research and development facilities.

The regime's production is said to focus on Sarin gas and VX, one of the deadliest chemical agents ever manufactured.

VX nerve agent is listed by the United Nations as a weapon of mass destruction. A single drop on the skin can kill within minutes.

Malaysian police have found traces on swabs taken from the eyes and skin of Kim Jong-Nam, the elder half-brother of North Korea's leader, Kim Jong-Un.

Mr Kim reported feeling sick and dizzy after being attacked by two women at Kuala Lumpur International Airport on 13 February. He was taken to the terminal's clinic, but died before reaching the hospital.

One of the female suspects also showed signs of exposure to VX.

Seven North Korean men are wanted as suspects in the case, including a diplomat from the country's embassy in Kuala Lumpur, in addition to the four people already in custody.

As well as its chemical weapons capability, North Korea is thought to have access to a wide range of biological weapons, including blister agents, anthrax, smallpox, cholera, and a form of plague.

It also has the means of delivery.

South Korea's government estimates half of Pyongyang's long-range missiles, and almost one-third of its artillery pieces can be fitted with chemical or biological warheads, although the degree to which those biological payloads would survive impact is unclear.

What is clear is that North Korea is continuing to pursue its weapons programme at pace, in spite of the sanctions and UN security resolutions against it.

If you had an impression previously of North Korea as a rogue state, with an unpredictable ruler and nuclear ambitions, you might want to upgrade your anxiety level.

North Korea is an increasingly isolated state, with an unpredictable ruler, who has nuclear ambitions, biological weapons and access to one of the world's most deadly chemical warfare agents.