China has told North Korean companies operating in its territory to close down as it implements United Nations sanctions against the reclusive state.
The companies will be shut by early January. Joint Chinese and North Korean ventures will also be forced to close.
China, Pyongyang’s only major ally, has already banned textile trade and limited oil exports.
The move is part of an international response to North Korea’s sixth and most powerful nuclear test.
The UN Security Council, of which China is a member, voted unanimously for fresh sanctions on 11 September.
China’s commerce ministry said it had set a deadline of 120 days from the passing of the resolution for any North Korean companies within its borders to close.
North Korea is politically and economically isolated, and the vast majority of its trade is with China.
Beijing has traditionally been protective of its neighbour, but has sharply criticised its nuclear tests and escalating rhetoric.
Earlier this year, it clamped down on its purchase of coal from Pyongyang and on seafood and iron trade across the border.