SEOUL, South Korea — The younger sister of the North Korean leader, Kim Jong-un, was shown in the North Korean media wearing a ring on her left ring finger on Friday, prompting speculation that she may have recently married.

Mr. Kim’s sister, Kim Yo-jong, believed to be in her late 20s, wore what appeared to be a gold ring in a photograph published by the Rodong Sinmun, the official newspaper of the North’s ruling Workers’ Party, on Friday. In the photograph, she was accompanying her brother on a visit to a nursery in Pyongyang, the North’s capital.

Shortly after the photograph appeared, the South Korean news agency Yonhap quoted anonymous North Korea sources in China as saying that Ms. Kim had married a son of Choe Ryong-hae, one of Mr. Kim’s closest aides, last year. South Korean officials could not immediately confirm the report.

Ms. Kim has emerged as an important party official since her brother took power after their father’s death in 2011. In November, the state-run media revealed that she was a deputy departmental director in the party. She is the only other member of Mr. Kim’s reclusive family whose official title in his government has been disclosed.