The bloc has agreed a new package of measures, including a ban on investments in North Korea and on European Union exports of oil, the sources said on condition of anonymity.
EU members also want to blacklist more North Korean individuals and entities, a move that would freeze their assets in the bloc and ban them from entering its territory.
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Ambassadors from the 28 member states on Thursday "agreed on a package of new autonomous measures", an EU official told AFP, and they will now be prepared in detail to be formally approved by a meeting of European foreign ministers next month.
The EU plans to reduce how much money North Korean workers in Europe can send home -- seen as a key source of vital foreign exchange revenue -- from its current level of 15,000 euros.
It also intends to expand the list of luxury products -- much loved by top officials in Pyongyang -- banned from export to the North. A cut in the number of North Korean workers in Poland from 500 to 300 is also on the cards, the sources said.
The North carried out its sixth nuclear test -- and most powerful to date -- on September 3, sparking international outrage and a fresh round of sanctions.
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International powers hope that economic sanctions will deprive the North of the resources it needs to pursue its nuclear programme and pressure it into negotiating.
The EU's latest move comes as US President Donald Trump paved the way for sanctions against foreign companies doing business with North Korea.
Trump said he had signed an executive order allowing sanctions against "individuals and companies that finance and facilitate trade with North Korea."
The measure could force Chinese banks or Russian importers to decide between doing business with North Korea or being blacklisted by the United States.
