South Korean media say North Korea has created a new No.2 post directly under leader Kim Jong Un as part of the hierarchy of the ruling Workers' Party.
The Yonhap news agency on Tuesday quoted sources as saying that the party revised its rules to create the post of "first secretary" at a party gathering in Pyongyang in January.
Kim Jong Un used the title for about four years from 2012.
Yonhap quotes the sources as saying that the person elected to the position will be able to preside over key party meetings on behalf of the leader.
The sources say a close aide to Kim, Jo Yong Won, appears to have been elected to the post.
Jo is a member of the politburo's standing committee. Footage that shows him accompanying Kim on tours of inspection has been aired on television a number of times.
South Korean evening newspaper Munhwa Ilbo quotes government sources as saying that the title "first secretary" has not appeared in North Korean media reports, and notes that Seoul is analyzing the situation with various possibilities in mind.