The US has unveiled fresh sanctions against North Korea which it says are designed to stop its funding of nuclear and ballistic missile programmes.
The measures target North Korean shipping operations and Chinese companies that trade with Pyongyang.
It comes a day after US President Donald Trump redesignated North Korea as a state sponsor of terrorism.
The North is already subject to a raft of sanctions from the US, the UN and the EU.
The US has been imposing sanctions on Pyongyang since 2008, freezing the assets of individuals and companies linked to its nuclear programme and banning the exports of goods and services to the country.
Three Chinese companies accused of trading with North Korea - Dandong Kehua Economy and Trade, Dandong Xianghe Trading and Dandong Hongda Trade - are added to the US Treasury's sanctions list.
Also targeted is the Korea South-South Co-operation Corporation which is alleged to have created revenue for the North by sending workers to countries including Russia, Poland, Cambodia and China.
In September, the US proposed a range of United Nations sanctions against North Korea, including an oil ban and a freeze on leader Kim Jong-un's assets.
It followed the North's sixth nuclear test and repeated missile launches.