Russia has begun sending home thousands of North Korean labourers who have worked in “slave-like” conditions to fund Kim Jong-un's regime.

In a volte-face on a practice dating to Soviet times, Moscow's ambassador to Pyongyang said on Wednesday several Russian regions had started sending back North Korean workers.

The new ban will be a “blow to the Russian economy,” ambassador Alexander Matsegora told state news agency RIA Novosti.

He said it was being done to comply with sanctions adopted by the United Nations security council last year over North Korea's nuclear weapons programme, including a prohibition on giving new visas to its workers abroad.

Russia issues 12,000-15,000 visas to North Koreans each year, and 35,000 North Koreans have been working here, mostly in construction, agriculture and fishing, Mr Matsegora added.