"Guided" by leader Kim Jong-un at the venue in Pyongyang on Saturday, it was to discuss important matters in "the building of the state and national defence," the North's official Korean Central News Agency (KCNA) said in a report.
The plenary meeting of the party's Central Committee has been a key focus of attention, as Pyongyang has set the year-end deadline for Washington to offer concessions in stalled nuclear talks, reports Yonhap News Agency.
Pyongyang has threatened to take a "new way" unless US President Donald Trump's administration brings a fresh offer.
"The immediate orientation of the struggle of the Party of Korea WPK (Workers' Party of Korea) and the state and important policy issues for new victory in our revolution under the present situation were brought up as agendas of the plenary meeting," the KCNA report said.
The meeting was held to "overcome the manifold and harsh trials and difficulties and further accelerate the development of the revolution with transparent anti-imperialist independent stand and firm will", it said.
The report added that the session came at a "watershed" time of when a "new historic transformation" is taking placing in relevant undertakings.
The KCNA said the plenary meeting "goes on", suggesting it will be a multiple-day meeting. It however, did not provide any other details.
Saturday's plenary meeting came a week after Pyongyang convened a meeting of the ruling party's central military commission and discussed "important organizational and political measures and military steps to bolster up" the armed forces, reports said Yonhap News Agency.
It was held ahead of a highly anticipated New Year's Day address that the North's leader is expected to deliver on Wednesday.
Speculation has mounted that North Korea could launch a long-range missile as a "Christmas gift" for Washington.
Christmas passed without such a test, but the US and South Korea have been on high alert for the North's possible major provocations.
( With inputs from IANS )