North Korea says it is facing its worst drought in a century and the United Nations has warned of the danger of mass starvation.

One of the few sources of badly-needed cash, is to supply overseas labour, so President Kim Jong-un has expanded the number of worker brigades sent abroad.

Tens of thousands of North Korean labourers now work in Russia, many of them in the construction industry, in the remote far east of the country.

Human rights groups say it is a form of slave labour.

Stephen Sackur sent this exclusive report from Vladivostok on Russia's eastern coast.