Because North Korea rarely publicizes the executions of top officials, most such reports cannot be independently confirmed. And doubts about General Ri’s supposed execution emerged in the weeks that followed. In March, a South Korean cable channel, MBN, reported that General Ri had been demoted, not executed, and that he had been allowed to return to service.

Pictures released Tuesday by the North Korean state news media seemed to support that theory. General Ri was shown wearing a three-star rather than a four-star insignia, indicating he had been reduced in rank.

South Korean intelligence officials say it is extremely difficult to get reliable information about developments within the North’s opaque government. Officials have disappeared from public view for months at a time, only to resurface later. Early last year, South Korean officials told reporters that Ma Won-chun, a senior general who was in charge of the renovation of the Pyongyang airport, had been purged. But General Ma, it appears, was simply demoted, and he resurfaced later in the year.

On Tuesday, North Korea organized a rally of hundreds of thousands of people in central Pyongyang to mark the end of the party congress. Mr. Kim, accompanied by his newly appointed senior aides, oversaw the rally, which featured parades and slogans of loyalty to his leadership, according to the state news media.