ALMATY (Reuters) - Islam Karimov, the 78-year-old president of Central Asia’s most populous country, is undergoing hospital treatment, Uzbekistan’s government said on Sunday, in a rare statement about the health of a reclusive leader who lacks an obvious successor.

FILE PHOTO - Uzbekistan's President Islam Karimov makes a statement at the Kremlin in Moscow, April 15, 2013. REUTERS/Grigory Dukor/File Photo

A government statement did not say what Karimov was being treated for or how serious his illness was, but official statements on his health are very uncommon.

“According to specialists, full health screening and further treatment will take a certain period of time,” it said.

Karimov, whose ex-Soviet nation of 32 million people borders Afghanistan, has been Uzbek leader since the collapse of the Soviet Union in 1991 and wields sweeping powers.

The absence of strong political institutions means that the eventual transition of power in the mostly Muslim nation may lead to confrontation within the elite or even destabilise the country which has long been targeted by Islamist militants.

Uzbekistan will celebrate its 25th anniversary of independence on Sept. 1 and the otherwise reclusive Karimov has routinely attended such celebrations, even occasionally dancing in public.

NO HEIR APPARENT

Karimov secured a fresh five-year term last year with 90.4 percent of the vote in an election that Western observers criticised for lacking genuine opposition.

He has no sons, who might have been regarded as heirs apparent in the patriarchal culture. His elder daugher, Gulnara, has not appeared in public since several media including the BBC reported in 2014 that she had been placed under house arrest.

Karimov’s second daughter, Lola Karimova-Tillyaeva, is Uzbekistan’s ambassador to Paris-based UNESCO.

Uzbekistan accounts for half the total population of Central Asia, a region made up of former Soviet republics where Russia, China and the West have competed for influence since the 1990s.

Although it exports gas, cotton and gold, Uzbekistan has struggled to keep up, in terms of average incomes, with its wealthier neighbours such as oil exporter Kazakhstan. About 2 million Uzbeks work abroad, mostly in Russia, to provide for their families.

In the 1990s, armed gunmen of the Islamic Movement of Uzbekistan challenged the Tashkent government but most of them have since left the country, moving to Afghanistan where they fought alongside the Taliban.

Some have now pledged allegiance to the Islamic State militant group which is estimated to have hundreds of Uzbeks among its fighters.

The government has accused Islamists of being behind protests in the city of Andizhan where police and security forces fired into a crowd in 2005, killing 187 people, according to official reports.

The crackdown soured Uzbekistan’s ties with the West, although Tashkent has since provided logistical assistance to NATO operations in Afghanistan. Tashkent is also at odds with most of its ex-Soviet neighbours due to disputes over territory and water resources.