North Korean leader Kim Jong Un
North Korean leader Kim Jong Un gives field guidance at the October 8 Factory in this undated photo released by North Korea's Korean Central News Agency in Pyongyang on Aug. 31, 2014. Reuters/KCNA

North Korean leader Kim Jong Un was not on the list of dignitaries for Friday's anniversary of the ruling Workers' Party founding, marking his first absence from the event in three years. The leader's absence has spurred further speculation about his health and a potential leadership vacuum.

Kim has been absent from public events for a month and there have been no references to his activities or whereabouts in local newspapers for the past few weeks, which typically track his movements. The 31-year-old Kim has reportedly attended the anniversary ceremony every year since he came to power, after his father’s death, in 2011. And his disappearance from public view has led to several theories about who might be in charge of the reclusive nation, while some reports have suggested that the leader has left his sister in charge.

At the event held Friday, officials from his government attended the party’s 69th anniversary celebrations and said that the might of the party “is growing stronger under the seasoned guidance of Marshal Kim Jong Un," according to Associated Press.

Lim Byeong-Chul, a spokesperson for Seoul's Unification Ministry, said: "There are continuous reports (in North Korea's state media) concerning the exercise of Kim Jong-Un's leadership," according to Agence France-Presse, or AFP, adding: "Judging from these, it seems that Kim Jong-Un is ruling normally.”

Kim was last seen publicly on Sept. 3, when he attended a music concert in Pyongyang with his wife.

Chung Young-Chul, a professor of North Korean studies at Sogang University in Seoul, said, according to AFP: "My own feeling is that there has been a health problem, but not a particularly serious one," adding: "A no-show would certainly force us to consider the possibility that it's more serious than we thought."

According to Reuters, the leader seems to have injured his ankle.

"He ordered all the generals to take part in drills and he took part too. They were crawling and running and rolling around, and he pulled a tendon," a source told Reuters, adding: "He injured his ankle and knee around late August or early September while drilling because he is overweight. He limped around in the beginning but the injury worsened."