"A doctor in KFSH leaked the following message," he wrote.
"An important person currently in ICU is:
- In critical condition
- Renal failure
- Congested Lungs (ARDS)
- Survival: probably days not weeks
- Medical team fully isolated
- Nearest relative is very nervous and aggressive," Mujtahidd tweeted.
In the past recent days, unofficial media and social media users have reported the death of Salman bin Abdulaziz Al Saud, while official Saudi Arabian media have confirmed his good health.
King Salman was admitted to King Faisal Specialist Hospital in the country's capital Riyadh on Monday for tests due to inflammation of his gallbladder.
He underwent a reportedly successful surgery to remove his gallbladder on Thursday.
HJ/