North Korean leader Kim Jong-un speaks at the congress of the ruling Workers' Party in Pyongyang on Sunday, state media reported Monday. Yonhap

North Korea has endorsed leader Kim Jong-un as the general secretary of the ruling Workers' Party at its ongoing congress, state media said Monday, in an apparent move to tighten his grip on power.

The election took place at the sixth-day session of the party's eighth congress in Pyongyang on Sunday, following the North's revision of party rules to reinstate the secretariat system that was scrapped in 2016, according to the North's official Korean Central News Agency (KCNA).

"The 8th Congress ... unanimously adopted a decision on electing Kim Jong-un as general secretary of the Workers' Party of Korea in reflection of the unanimous will and desire of all the delegates and other Party members, all the people and service personnel of the People's Army," the report said.

The general secretary title was previously held by Kim's late predecessors, his grandfather Kim Il-sung and father Kim Jong-il.

Since Kim took office following his father's death in late 2011, the North has called Kim Jong-il the "eternal general secretary" of the party and Kim Il-sung the "eternal president" of North Korea.

During an election that took place the same day, Kim's younger sister, Kim Yo-jong, was not included as an alternate member of the party's powerful political bureau.

Speculation has swirled that the younger Kim, previously an alternate member of the politburo, could be promoted to a higher position as she appeared to have undertaken a prominent role in inter-Korean affairs and other key issues.

Jo Yong-won, a senior party official who was often spotted accompanying the leader during his field trips last year, was promoted to a member of the presidium of the political bureau, a position held by only five people in the North including leader Kim.