With North Korea saying nothing so far about the disappearance of Kim Jong-un, who may be unwell, there's renewed worry about who's next in line to run the nuclear-armed country that's been ruled by the same family for seven decades.
Questions about Mr Kim's health flared after he skipped an April 15 commemoration of the 108th birthday of his grandfather, North Korea founder Kim Il Sung.
It's North Korea's most important event, and Mr Kim (36) hadn't missed it since inheriting power from his father in late 2011.
North Korea's state media yesterday said Mr Kim sent a message thanking Syria's president for conveying greetings on his grandfather's birthday, but didn't report any other activities, while rival South Korea repeated that no unusual developments had been detected in the North.
Mr Kim has been out of the public eye for extended periods in the past, and North Korea's secretive nature allows few outsiders to assert confidently whether he might be unwell, let alone incapacitated. Still, questions about the North's political future are likely to grow if he fails to attend upcoming public events.
Mr Kim is the third generation of his family to rule North Korea, and a strong personality cult has been built around him, his father and grandfather. The family's mythical "Paektu" bloodline, named after the highest peak on the Korean Peninsula, is said to give only direct family members the right to rule the nation.
That makes Mr Kim's younger sister, senior ruling party official Kim Yo-jong, the most likely candidate to step in if her brother is gravely ill, incapacitated or dies. But some experts say a collective leadership, which could end the family's dynastic rule, could also be possible.
"Among the North's power elite, Kim Yo-jong has the highest chance to inherit power, and I think that possibility is more than 90pc," said analyst Cheong Seong-Chang.
"North Korea is like a dynasty, and we can view the Paektu descent as royal blood so it's unlikely for anyone to raise any issue over Kim Yo-jong taking power."
Believed to be in her early 30s, Kim Yo-jong is in charge of North Korea's propaganda affairs, and earlier this month was made an alternate member of the powerful Politburo.
She has frequently appeared with her brother at public activities, standing out among elderly male officials.