Here are the key steps in Pyongyang's banned military programmes, that have seen multiple sets of sanctions imposed on the regime.

North Korea starts working in the late 1970s on a version of the Soviet Scud-B missile with a range of around 300 kilometres (200 miles), carrying out a first test in 1984.

Between 1987 and 1992, it begins developing longer-range missiles, including the Taepodong-1 (2,500 km) and Taepodong-2 (6,700 km).

The Taepodong-1 is test-fired over Japan in 1998 but the following year, Pyongyang declares a moratorium on such tests as ties with the United States improve.

It ends the moratorium in 2005, blaming the Bush administration's "hostile" policy, and carries out its first nuclear test on October 9, 2006.

In May 2009, there is a second underground nuclear test, several times more powerful than the first. Kim Jong Un succeeds his father Kim Jong Il -- who dies in December 2011 -- and oversees a third nuclear test in 2013.

Pyongyang carries out its fourth and fifth nuclear tests in January and September 2016.

In between, it test-fires a submarine-launched ballistic missile and launches a ballistic missile directly into Japanese-controlled waters for the first time.

The North carries out a series of missile launches, with progressively longer ranges and some falling into the Sea of Japan.

On July 4 it tests an ICBM capable of reaching Alaska, calling it an independence day gift for "American bastards".

Hours after US President Donald Trump threatens Pyongyang on August 8 with "fire and fury", the North says it is considering launches towards US strategic military installations in Guam.

On September 3, North Korea conducts its sixth and by far its largest nuclear test. Estimates of the yield vary with some ranging as high as 250 kilotons, 16 times the size of the 15-kiloton US bomb that destroyed Hiroshima in 1945.

On November 20, Washington declares North Korea a state sponsor of terrorism, a day before hitting the isolated regime with fresh sanctions.

The same month, the North launches a new Hwasong-15 ICBM, which analysts agree is capable of reaching the whole US mainland, although they voice scepticism that Pyongyang has mastered the advanced technology needed to allow the warhead to survive re-entry into the Earth's atmosphere.

In his New Year speech in 2018, Kim says the North has completed the development of its nuclear force.

South Korean President Moon Jae-in uses the Winter Olympics in his country to catalyse a rapid diplomatic thaw on the peninsula.

At a party meeting on April 20, Pyongyang declares a moratorium on nuclear blasts and ICBM launches and says the atomic test site at Punggye-ri is no longer needed and will be dismantled.

In May the North invites a handful of foreign media to see the site's entrances blown up.

At his landmark summit with the US president in Singapore on June 12 last year, Kim signs a vague deal on the "denuclearisation of the Korean peninsula".

But in the following months both sides disagree about what the term means.

After a summit between Moon and Kim in Pyongyang in September, the South Korean leader says the North has offered to dismantle a key nuclear complex in Yongbyon -- if the US takes "corresponding measures".

A 2019 report by the Stanford Center for International Security and Cooperation says Pyongyang has continued to produce nuclear material, estimating its arsenal at 35 to 37 atomic bombs.