The National Intelligence Service (NIS) told MPs its assessment was not based on circumstantial inference but on what it described as "credible intelligence" collected by the agency, according to briefings by ruling and opposition party members after a closed-door parliamentary meeting.
The NIS said the imagery of the daughter driving a tank was intended to highlight her supposed military aptitude and dispel doubts over a female heir, MPs said on Monday.
North Korea's state-run media KCNA in March published photos of Kim and his daughter driving a new tank, following earlier images showing her firing a rifle at a shooting range and using a handgun.
Such scenes are intended to pay "homage" to Kim's own public military appearances during the early 2010s when he was being prepared to succeed his own father, ruling Democratic Party MP Park Sun-won said.
The latest assessment of Kim's daughter, who is believed to be about 13 and to be named Ju Ae, is a progression from earlier analysis by the spy agency, which said she was likely being groomed to succeed her father.
Ju Ae's repeated presence at defence-related events is aimed at easing doubts over a female successor and accelerating the construction of a succession narrative, the MPs said, citing the NIS.
MPs have previously said the agency believes her increasingly prominent role suggests she is already being treated as the de facto second-highest figure in the North's leadership.
People Power Party MP Lee Seong-kweun said the NIS noted that suggestions Kim's younger sister Kim Yo Jong might be unhappy about the focus on Ju Ae were misplaced, as Kim Yo-jong did not hold independent power.
Some North Korea experts, however, urged caution in interpreting the images as definitive succession signals.
Hong Min, an analyst at the Korea Institute for National Unification, said Ju Ae's tank appearance alone was insufficient to conclude she had been confirmed as Kim's heir, noting she appeared alongside her father rather than independently, unlike Kim Jong-un's own solo military appearances during his grooming phase.
