North Korea's state news agency KCNA said on Saturday leader Kim Jong-un attended the completion of a fertilizer plant in a region north of the capital, Pyongyang, in the first report of his public activity since April 11.
Reuters could not independently verify the KCNA report.
KCNA reported that Kim cut a ribbon at the ceremony on Friday and those attending the event "burst into thunderous cheers of 'hurrah!' for the Supreme Leader who is commanding the all-people general march for accomplishing the great cause of prosperity."
Kim expressed satisfaction about the production system of the fertilizer factory, saying the plant made significant contribution for the progress of the country's chemical industry and food production, KCNA said.
Kim was accompanied by several senior North Korean officials, including his younger sister Kim Yo Jong, KCNA said.
US President Donald Trump said after the KCNA report that he will have something to say about Kim at the appropriate time.
There has been speculation about Kim's health after he missed the birth anniversary celebrations of state founder Kim Il Sung on April 15. The day is a major holiday in North Korea and Kim as leader usually pays a visit to the mausoleum where his grandfather lies in state.
Earlier, a source familiar with US intelligence analyses and reporting said that US agencies believed that Kim Jong-un is not seriously ill and that he still very much remains in power.
"We think he's still in charge," the source said on condition of anonymity.
The source could not immediately confirm the KCNA report.
The White House and State Department did not immediately respond to requests for comment.