Platinum Jubilee: North Korea's Kim Jong Un congratulates Queen Elizabeth II

North Korea says its leader, Kim Jong Un, sent a letter congratulating Queen Elizabeth II as Britain began a four-day celebration marking her 70 years on the throne.

North Korea's Foreign Ministry said on its website that Kim sent a letter congratulating the queen and the British people. It didn't provide further details.

North Korea and Britain established diplomatic relations in 2000 and have maintained embassies in each other's capitals despite a steady decline in bilateral ties.

North Korea's relations with the West have worsened in recent years as it accelerated its nuclear weapons and missile development in a push to acquire an arsenal that could threaten the United States and its allies in Asia.

Kim Jong Un sent a letter congratulating Queen Elizabeth II. Photo / AP

North Korea has criticised Britain in recent years for supporting international sanctions against the North over its nuclear ambitions and human rights record, and for participating in a new US-led alliance to help Australia acquire nuclear-powered submarines.

Queen Elizabeth II smiles on the balcony during Trooping The Colour during the Platinum Jubilee. Photo / Getty Images

North Korea has conducted 17 rounds of missile tests in 2022, including its first intercontinental ballistic missile launches in nearly five years, as it pushes brinkmanship aimed at cementing its status as a nuclear power and negotiating economic and security concessions from a position of strength.

US and South Korean officials say there are signs North Korea is preparing to conduct its first test of a nuclear explosive device since 2017.