MOSCOW — Whether Uzbekistan’s president is at death’s door or has already passed through is unclear, but that may not be the greatest uncertainty facing the country — it’s what comes after his death.

As independent Uzbekistan’s only leader, Islam Karimov has run a monolithic regime, harshly repressing any opposition and cultivating no apparent successor. The government announcement Sunday that the 78-year-old Karimov had been hospitalized, and his daughter’s statement that he had suffered a brain hemorrhage, raised concern that the most populous of the ex-Soviet nations in central Asia could face prolonged internecine maneuvering among various clans to take power and that Islamic radicals could exploit the interregnum.

Some Russian analysts meanwhile worried that the United States could try to use a power vacuum to foment “color revolution” protests like those that drove out leaders in Georgia, Ukraine and Kyrgyzstan.

On Tuesday, unconfirmed reports claimed Karimov had already died. Russian news agencies reported that a major concert planned for the capital Tashkent on Wednesday to celebrate the 25th anniversary of independence from the Soviet Union had been called off — a possible echo of the Soviet practice of cancelling entertainment to signal a leader’s demise.

“It’s a place that runs on rumors,” said analyst Paul Stronski of the Carnegie Endowment for International Peace.

Uzbekistan’s opacity makes assessing the potential threat of Islamic extremism difficult, Stronski said. The Islamic Movement of Uzbekistan over the years has been affiliated with the Taliban, al-Qaida and the Islamic State group and its fighters active outside the country, but how much presence it has in Uzbekistan is unclear. The government may have overstated the Islamist threat to justify crackdowns on the opposition; the 2005 Andijan protests that ended with police killing hundreds were said by authorities to have been inspired by the IMU.

Although Uzbeks are largely poor and repressed, “we really don’t know the full level of discontent … we don’t know how much these (Islamist) groups have penetrated,” Stronski told The Associated Press. “It’s something to be concerned about in the longer term, but I don’t see it as imminent.”

“Islamists have influence, but very limited,” Vladimir Yevseyev, deputy director of the Institute for CIS Countries, a Moscow-based think tank studying ex-Soviet countries, was quoted as saying by the Tass news agency.

Analyst Adzhar Kurtov told Tass he believes that all of the possible successors to Karimov are “people with a very careful approach who will try to create a situation in this transition period that will not allow agitation and destabilization.”

Stronski also said he expects that amid whatever maneuvering there is for power post-Karimov, the threat of extremism won’t be sidelined. “I think generally they’re going to keep an eye on the ball,” he said.

Under the Uzbek constitution, if the president dies or relinquishes power, the president of the senate takes interim leadership for three months until new elections. But the senate president is seen as a pliant figure unlikely to seek the permanent presidency.

Prime Minster Shavkat Mirziyayev and a deputy prime minister, Rustam Azimov, are regarded as the best positioned to take over. Azimov, who is also finance minister, is viewed as likely the more liberal of the two.

But in a country with no genuinely democratic experience, the force of the constitution can be open to question. In the region’s only analogous transfer of power, the death of Turkmenistan’s president in 2006, power was to pass to the head of the parliament, but he was jailed and the health minister took over.

In the view of Alexei Martynov, a pro-Kremlin analyst in Moscow, Uzbekistan should be on guard against another threat.

“U.S. political technologists who were behind the abortive coup in Uzbekistan in 2005 may feel the temptation to have another try,” he was quoted as saying by Tass. “The Uzbek security services should pay the closest attention to the U.S. embassy in Tashkent, and keep an eye on what is happening there, who enters the building and who walks out of it and if the Americans are up to something.”