(CNN) Uzbekistan's first and only president has died, leaving an uncertain future for a government marred by controversy.

President Islam Karimov, who ruled Uzbekistan for 25 years, died Friday, the Uzbek government announced on the state-run news agency Uza. He was 78 years old.

Karimov had a stroke and was hospitalized Saturday, his daughter Lola Karimova-Tillyaeva announced on Facebook.

Friday, she posted a black square on her official Instagram account, with the message, "He left us."

A funeral will be held Saturday.

Russian President Vladimir Putin expressed his condolences in a statement on the Kremlin website Friday.

"It is difficult to overestimate the contribution of Islam Karimov to the establishment of relations of strategic partnership between our countries," the Russian President said.

"Under (Karimov's) guidance ... Uzbekistan held a peaceful foreign policy, contributed to the strengthening of security and stability in Central Asia and to the development of multilateral cooperation in the region," Putin added.

Karimov's death leaves the future of the resource-rich country in question, said Andrey Kortunov, president of the New Eurasia Foundation.

There is "no master plan, no successor who has been endorsed and accepted by everybody (in Karimov's inner circle)," Kortunov said.

Reign started in Soviet era

Karimov became leader of the Uzbek Soviet Socialist Republic in 1989. Two years later, he declared the independence of the Republic of Uzbekistan and assumed the presidency of the new country.

In 1995, his mandate was extended for another five years by referendum. Despite a two-term limit, he won re-election in 2000, 2007 and 2015.

International critics, including Human Rights Watch, said voters had no real choice in the elections because the government restricts opposing political activity.

In 2007, Karimov made Parade magazine's list of "World's Worst Dictators." In addition to violating the two-term limit, Parade said, "his government engages in routine torture of citizens and has subjected dissenters to forced psychiatric treatment."

Alleged human rights abuses

Human Rights Watch calls the country's human rights record "atrocious," saying "thousands are imprisoned on politically-motivated charges. Torture is endemic in the criminal justice system. Authorities continue to crack down on civil society activists, opposition members, and journalists."

Reporters Without Borders ranks Uzbekistan 166th out of 180 countries in terms of press freedom, noting that "Karimov subjects his country to the strictest censorship. No fewer than nine journalists are rotting in prison in the most abominable conditions."

Relationship with the US

Karimov's relationship with the United States grew after the 9/11 terror attacks, when Washington was trying to gain the cooperation of countries near Afghanistan during its hunt for al Qaeda leader Osama bin Laden.

Karimov agreed to allow US forces to use Uzbekistan's airspace and one of its airports.

In a joint statement, the two countries said they agreed "to establish a qualitatively new relationship based on a long-term commitment to advance security and regional stability."

But Karimov's relationship with the US took a hit in 2002, after a State Department report found Karimov's security forces tortured people, especially Muslims, under the guise of combating terrorism.

Report: Daughter pocketed $1 billion in bribes

Karimov was married with two adult daughters. His eldest daughter, Gulnara, allegedly pocketed $1 billion from foreign telecom companies trying to break into the Uzbek market, according to the Organized Crime and Corruption Reporting Project.

"Meanwhile, telecom users in her impoverished country pay among the highest rates in the world for mobile phone service," the OCCRP report found.

"Once anointed as the heir apparent to her ailing father, she has fallen from favor and is now under house arrest."