Bahrain's highest religious authority Sheikh Isa Qassim has been transferred to the intensive care unit after undergoing a second surgery in as many months.
The ailing cleric will reportedly be kept under close observation until Friday evening.
Sheikh Qassim was transferred to hospital earlier in the week after his health deteriorated.
According to a statement released by Bahrain's opposition Al-Wefaq party on Wednesday, the authorities "procrastinated" and "delayed" his transfer to hospital for ten days.
Sheikh Qassim, whose health has been gradually deteriorating in recent months, was arbitrarily stripped of his Bahraini nationality in June 2016. Since then he has lived under virtual siege, and in May 2017 Manama's security forces stormed his Diraz home and place him under house arrest.
The kingdom of Bahrain is home to roughly 1.2 million people, most of whom are Shiites, but the ruling family is from the Sunni minority.
Since 2011, Al Khalifa rulers had been embroiled in a brutal crackdown on all dissent, imprisoning or forcing politicians and activists into exile.
The tiny Gulf kingdom, an important ally of the US, is home to the US Navy's Fifth Fleet since 1995.
Source: Lualua TV, Edited by website team