Iraq's Grand Ayatollah Ali Al Sistani has fractured his left thigh bone, a source from his office said.
"His eminence was subjected to a twisting in the left leg that led to a fracture of the thigh bone, and he will be operated on today," a statement from a source in his office read.
It said that an Iraqi medical team will perform the operation.
The reclusive cleric's messages are usually delivered through a representative in his office.
He was taken to a hospital in southern Iraq, near his home in the holy city of Najaf.
Iraqi officials and diplomatic missions confirmed that Mr Al Sistani's operation was a success.
Outgoing Prime Minister Adel Abdul Mahdi said that the government was at Mr Al Sistani's disposal to provide him with necessary care “inside or outside Iraq immediately," according to a statement from his office.
The US embassy in Baghdad said it has received “with great joy” news of his successful surgery, noting his “ever-lasting stabilising role.”
Mr Al Sistani’s health is crucial to the stability of Iraq especially as the country is caught between US-Iran escalations following the killing of Quds Force commander Qassem Suleimani earlier this month.
It was the most serious escalation of tension between Washington and Tehran in years and raised fears of a full-scale conflict in the Middle East between the two foes.
The cleric was quick to denounce the attacks, calling it a "a violation of Iraq’s sovereignty" and added that no foreign powers should be allowed to decide Iraq's fate.
His comments and statements hold great sway over many Iraqis.
Mr Al Sistani is Iraq’s most influential Shiite cleric who has given a significant boost to the country’s protest movement.
Iraq has been rocked by anti-government protests that pushed Mr Al Sistani to urge authorities to address complaints made by the public.
Since last October, protesters, most of them young, are demanding an overhaul of a political system they see as profoundly corrupt and loyal to neighboring Iran.
Their demands were met with a violent government crackdown that killed hundreds and injured tens of thousands of civilians.
The government and militia forces supported by Iran turned their guns on the mostly Shiite protesters.
In response, Mr Al Sistani called on the government to enact a new election law and constitutional reforms; his most outspoken support for protesters who have taken to the streets in Baghdad and southern Iraq for more than three months.
He also urged parliament to reconsider its support for Mr Abdul Mahdi as the protests dragged on.
It pushed Mr Abdul Mahdi to announce his resignation in November, citing his response to the call made by Mr Al Sistani.
The Iraqi cleric had consistently backed the demonstrations but stopped short of directly challenging Mr Abdul Mahdi's government.
But the cleric changed tack following the deteriorating protest movement.
Almost every player in Iraq has had to take his views into account, especially as every government and prime minister since the fall of former dictator Saddam Hussein has had his approval.
