The office of Serbia's president says he has been hospitalized with cardiovascular problems.
The statement released Saturday says that Aleksandar Vucic was admitted to the military hospital in Belgrade, the capital, on Friday afternoon.
No other details were immediately available. Serbian media have reported in the past that the 49-year-old Vucic suffers from high blood pressure.
A former extreme nationalist during the 1990s' war in the former Yugoslavia, Vucic and his Serbian Progressive Party came to power seven years ago promising to take Serbia into the European Union.
The populist leader has since faced accusations of curbing media freedoms and democracy. Vucic's government has strengthened Serbia's close relations with traditional Slavic ally Russia.