Barack Obama has imposed new sanctions on North Korea’s economy after January’s test of a nuclear bomb, in a step that raises the pressure on China to follow suit.

The measures, the result of an executive order by the US president, target Pyongyang’s sources of external earnings from industries such as coal, which generates $1bn a year in revenues, in addition to transportation, financial services, energy and mining.

The US Treasury said in a separate announcement that US companies would be prohibited from trading with a range of North Korean companies it said were connected to North Korea’s weapons programmes. It named 17 North Korean entities and individuals and 20 ships that it believes are engaged in illicit weapons procurement, saying US companies would be prohibited from doing business with them.