Updated

A mysterious young woman appearing at the side of North Korea's new leader is the subject of speculation she could be Kim Jong Un's younger sister or even wife, but Pyongyang has released no details.

North Korean state TV on Sunday showed an elegant, somber young woman in a black jacket and skirt bowing with Kim at a ceremony marking the 18th anniversary of the death of his grandfather, North Korea founder Kim Il Sung.

She is believed to be the same woman shown Saturday seated next to Kim at a concert. North Korean state broadcaster KRT showed her walking into the concert hall behind Kim, and they clapped together at the end of Friday's performance.

The North's Rodong Sinmun newspaper on Monday ran a photo of Kim and the woman on its website without identifying her. Her appearances with Kim were front-page news in South Korean media.

Little personal information is known about Kim, and even his exact age has not been announced, although he is believed to be in his late 20s. His younger sister, Kim Yo Jong, was born in 1987, according to Cheong Seong-chang, a North Korea analyst at the Sejong Institute in South Korea.

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North Korean officials have refused to comment on speculation about Kim Jong Un's marital status, which has not been listed in official biographies for the young leader.

Kim has appeared regularly in state media since taking power in December after the death of his father, longtime leader Kim Jong Il, but he is mostly seen with powerful officials and with citizens and cheering soldiers during regular tours of factories, parks and military bases.

Two exceptions have been his aunt — Kim Jong Il's younger sister, Kim Kyong Hui — and his uncle Jang Song Thaek, both powerful figures in the government and key advisers. During Kim Jong Il's rule, Kim Kyong Hui often accompanied her brother at official functions.