MOSCOW — Uzbekistan’s government issued an unusual statement on Sunday announcing the hospitalization of President Islam Karimov, who has ruled the former Soviet republic in Central Asia for more than 25 years.

The statement gave no details about the nature of the illness suffered by the 78-year-old president or his condition, saying only that “in the opinion of the specialists, a full medical examination and subsequent treatment will require a certain amount of time.”

The Regnum news agency reported from Tashkent, the Uzbek capital, that police and security forces have formed a cordon around the government hospital where Karimov was being treated, in an apparent indication of the unease caused by his hospitalization. The cordon, which was established late Saturday, has a radius of several kilometers (a mile or two), the report said.

Karimov, who tolerates no dissent, has ruled Uzbekistan since Soviet leader Mikhail Gorbachev made him the republic’s Communist Party chief in 1989. In December 1991, just days after the Soviet Union ceased to exist, Karimov was elected president of the newly independent state.

As he has aged, questions have arisen about both a successor and the long-term stability of the strategically placed Central Asian country.

During the war in Afghanistan, Uzbekistan served as an important supply route for U.S. and NATO troops.

When the war began in 2001, Karimov allowed U.S. forces to use a major air base. He then evicted them in anger over U.S. criticism of a violent crackdown on a 2005 uprising in Andijan, where Uzbek troops fired on demonstrators, killing more than 700 people, according to witnesses and human rights groups. It was the world’s worst massacre of protesters since the 1989 bloodbath in China’s Tiananmen Square.

Karimov later quietly softened his position, allowing Uzbekistan to be part of the Northern Distribution Network, a vital supply route for Afghanistan in the final years of the war.