MOSCOW — The Uzbekistan government confirmed Friday that Islam Karimov, a ruthless autocrat who ruled Uzbekistan for almost three decades, had died in the Uzbek capital of Tashkent.

Karimov, who crushed an Islamic insurgency after surviving an assassination attempt by Islamic militants in 1999, was considered a bulwark against the spread of any jihadi threat in the region. With him gone, there is some concern that the Islamic State or other groups might try to exploit the transition to reemerge.

A joint statement by the Cabinet of Ministers and the Parliament said Karimov, 78, died earlier Friday after a stroke that led to multiple organ failure.

The announcement came after a long, strange interlude during which Uzbek officials refrained from confirming the death even while the leaders of Turkey and Georgia expressed condolences, mosque leaders were barred from offering prayers for the president’s health, and funeral arrangements were being made publicly.

A respected opposition website posted pictures of cemetery workers in Samarkand, the president’s hometown, digging a fresh grave in a prominent location.

The most likely reason for the official silence was that top government officials had been unable to decide on the succession and did not want to announce that Karimov was dead until they could also say who would replace him, at least temporarily.

The official statement said the prime minister, Shavkat Mirziyoyev, who is widely deemed to be the president’s most likely successor, would lead the funeral Saturday and Karimov would be buried in Samarkand in accordance with Muslim rites.

Long in poor health, Karimov had a stroke Aug. 27, ending what was often described as one of the most brutal reigns to emerge from the collapse of the Soviet Union, exemplified by its continued use of forced labor for Uzbekistan’s annual cotton harvest.

The circumstances of his death remain murky. The first hint that he was critically ailing came in a government statement Sunday saying he had been hospitalized. It gave no other details. But in a Facebook post, his younger daughter, Lola Karimova-Tillyaeva, Uzbekistan’s ambassador to UNESCO in Paris, said he had had a brain hemorrhage.

It is by no means certain that Mirziyoyev, who is considered a Kremlin ally, will succeed Karimov. Rustam Azimov, a deputy prime minister and finance minister, is a possible technocratic alternative.

Karimov’s older daughter, Gulnara Karimova, had once been seen as having a promising political future, but those prospects disintegrated in a public soap opera involving charges of bribery, money laundering, physical violence, and even sorcery.

Karimov rose through the ranks of the local Communist Party until the Soviet leader Mikhail S. Gorbachev named him first secretary and effectively Uzbekistan’s chief in 1989. He won a presidential election after independence in 1991 and used Soviet methods to govern the country.

“He is the state and the state is him, and it has been that way for at least 25 years,’’ said Steve Swerdlow, director of Central Asia research at Human Rights Watch.

Power in Uzbekistan was concentrated in the hands of the National Security Service, modeled on the old KGB of the Soviet Union. Its longstanding but reportedly ailing director, Rustam Inoyatov, is expected to wield the greatest influence in the selection of the next president.

The president’s widow, Tatyana Karimova, an economist, also holds considerable sway. Neither is known to be seeking a public role.

“It is a police state where the power belongs completely to the security services,’’ said Daniil Kislov, the Moscow-based editor-in-chief of the website Ferghana.ru. “The special services will not allow for any alternative on the succession.’’

An estimated 1 million Russians still live in Uzbekistan, though the population of more than 31 million is overwhelmingly Sunni Muslim.

“Whether or not the Islamic State sees a succession as an opportunity to create risks for the much-hated Russians remains an open question,’’ said Cliff Kupchan, an expert on Russia and chairman of the Eurasia Group, a risk advisory firm based in Washington.

In 1999, Karimov made his position toward radical Islam abundantly clear.

“I am prepared to rip off the heads of 200 people, to sacrifice their lives, in order to save peace and calm in the republic,’’ he told reporters. “If my child chose such a path, I myself would rip off his head.’’

He went on to prove it, massacring hundreds of antigovernment demonstrators in 2005 in the town of Andijon, a center of ethnic, social and economic tension in the fertile Fergana Valley. Both Europe and the United States imposed military sanctions.

Karimov responded by expelling US forces from Karshi-Khanabad Military Base, an important link in the supply chain for the forces propping up the government in Afghanistan against the Taliban.

Supply needs eventually trumped human rights issues, and the United States restored relations, even giving the Uzbekistan forces hundreds of surplus armored vehicles as US forces in Afghanistan were being drawn down.

Islam Karimov was born on Jan. 30, 1938, in Samarkand, Uzbekistan. His official biography said his father had been an office worker. Other accounts suggested that his parents, overwhelmed by a large family and meager resources, put him in an orphanage, at first temporarily, but eventually left him there.

He studied to become an engineer, worked at an airplane factory, and joined the Communist Party in the early 1960s. He married in 1964, and he and his wife had a son, Petr, but soon divorced. The son is believed to have moved to Moscow decades ago and never returned.

Karimov joined Gosplan, the central Soviet economic planning agency, in 1966 and married for the second time in 1967. He rose to become the finance minister for the Soviet Socialist Republic of Uzbekistan in 1983.

Karimov leaves his wife and daughters, as well as four grandchildren.