"I would propose to ministers today to strengthen economic pressure on North Korea, supporting a new UN Security Council resolution adopting tougher economic measures, starting new autonomous European Union sanctions on North Korea, and working with other partners in the world to make sure that everybody implements fully and strictly the already decided economic measures," Mogherini said in a statement made at the arrival to the informal meeting of EU foreign ministers.

The high representative stressed that no official decision will be made in Tallinn as Thursday's meeting is an informal one.

"The EU took a very firm and united position in July already," Mogherini said. "Today we are facing a different level of threat that is clearly a threat to global peace and security and to the entire non-proliferation regime.

"The EU has always been convinced that economic pressure alone is never sufficient," she continued. "That is why, on our part, we have always offered our regional and international partners, the international community and even the [Democratic People's Republic of Korea] the path of dialogue. We believe that more economic pressure in this respect, and more diplomatic pressure in this respect, could make a difference. In any case, it must be pursued, because other alternatives, in our view, could be extremely dangerous."

As reported by CNN, NBC and other news outlets, North Korea announced over the weekend that it had successfully conducted the test of a hydrogen bomb — the country's sixth — on Sept. 3, the explosion of which created a magnitude-6.3 tremor.