Iran's supreme leader Ayatollah Ali Khamenei had a prostate operation on Monday, the state news agency Irna said.
"The operation took place with success," said the agency.
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"I am going to hospital to undergo an operation. There is nothing to worry about," Khamenei was reported as saying.
"This does not mean that people are not praying ... but it is a normal operation."
Aged 75, Khamenei has led Iran for 25 years, replacing Ruhollah Khomeini, who founded the Islamic Republic of Iran.