MOSCOW (AFP) -- Uzbekistan will bury President Islam Karimov Saturday, as his death plunges the Central Asian nation into the greatest period of uncertainty in its post-Soviet history with no clear successor to the iron-fisted ruler.

Karimov was pronounced dead late Friday after he suffered a stroke last weekend and fell into a coma, following days of speculation that authorities were delaying making his death public.

The strongman's funeral will be held in his home city of Samarkand, central Uzbekistan, on Saturday morning and the country will begin three days of mourning.

Russian Prime Minister Dmitry Medvedev is expected to fly in for the funeral, along with a coterie of leaders from former Soviet republics including Tajik President Emomali Rakhmon, Turkmen President Gurbanguly Berdymukhamedov and the prime ministers of Kyrgyzstan, Belarus and Kazakhstan.

Karimov's body was to be flown to Samarkand airport, which on Saturday will be closed to all flights except those with special permission.

The funeral cortege was expected to leave the airport at 6 am local time (0100 GMT). His coffin will be displayed in a city square from 9 am for people to pay their last respects before being buried in a nearby cemetery, Russian news agencies reported, citing local officials.

Loyalist Prime Minister Shavkat Mirziyoyev is heading the organisation committee for the funeral, suggesting that he could be in line to take over long-term from Karimov.

Under Uzbek law, senate head Nigmatulla Yuldashev should now become acting president until early elections are held.

Karimov, 78, was one of a handful of Soviet strongmen who clung to power after their homelands gained independence from Moscow in 1991.

His brutal quarter century rule earned him a reputation as one of the region's most brutal despots who ruthlessly stamped out opposition.

The most serious challenge to his rule came in the guise of his eldest daughter, once seen as a possible heir, who he put under house arrest in 2014 after a family power struggle broke into the open.

Uzbekistan has never held elections deemed free and fair by the international monitors, and Karimov won his fifth terms in office last March with 90 percent of the vote.

His death pushes the strategically located landlocked country into a "phase of uncertainty", the head of the Russian lower house of parliament's international affairs committee, Alexei Pushkov, said Friday.

Rights groups -- which have long accused Karimov's regime of the most serious abuses including torture and forced labour in the lucrative cotton industry -- have slammed his time in power as a catastrophe for Uzbekistan.

But Karimov portrayed himself as guarantor of stability and bulwark against radical Islam on the borders of Afghanistan, crushing fundamentalist groups in the majority Muslim republic.

"Islam Karimov leaves a legacy of a quarter century of ruthless repression," said Steve Swerdlow, Central Asia researcher at Human Rights Watch.

"Karimov ruled through fear to erect a system synonymous with the worst human rights abuses: torture, disappearances, forced labour, and the systematic crushing of dissent."

Despite Karimov's brutal record, Uzbekistan still receives US aid and both Secretary of State John Kerry and Russian leader Vladimir Putin have jetted in for talks over the past year.

As world powers continue to vie for influence, activists question how the nation's rights record can ever improve.