Uzbekistan's interim leader Shavkat Mirziyoyev has won a crushing presidential election victory to succeed the late strongman Islam Karimov,official results showed Monday.

The Central Election Commission said Mirziyoyev scooped 88.6 percent of the Sunday vote, according to a preliminary count, while Western monitors reported signs of fraud.

Mirziyoyev's massive margin over rivals for the five-year term echoed the past successes of predecessor Karimov, who died of a stroke in September after 27 years at the helm of the commodity-rich country.

A mission led by the Organisation for Security and Cooperation in Europe said there were "indications of ballot box stuffing and widespread proxy voting" during the vote.

"The dominant position of state actors and limits on fundamental freedoms undermined political pluralism and led to a campaign devoid of genuine competition," mission head Peter Tejler said at a press conference broadcast online from the Uzbek capital Tashkent.

Russian President Vladimir Putin "warmly congratulated" Mirziyoyev on his victory in a phone conversation, the Kremlin said in a statement.

Mirziyoyev, a Karimov loyalist who was named as his prime minister in 2003, seemed to face little actual competition in the vote. Two of his election rivals were the same pro-regime candidates that Karimov himself had faced in the last presidential election in 2015.

"The format for Uzbek elections has not changed since Karimov's death, because the regime has not had time to think of anything different," said Kamoliddin Rabbimov, an Uzbek political analyst who lives in France.

- 'Everything has changed' -

In the run-up to Sunday's poll, Mirziyoyev, 59, created an online forum for public complaints and pledged to prioritise economic reforms as many Uzbeks struggle to eke out a living.

The election commission published a series of glowingly optimistic quotes attributed to voters about the poll.

"I realised the importance of my voice in the future development of the country which made me proud," student Sevara Foziljonova was quoted as saying on the commission website.

"There was a time when we had to agree with everything," a man named as 106-year old World War II veteran Badal-bobo Khuramov was quoted as saying, referring to the Soviet era.

"Now everything has changed," said the man, described by the commission as a grandfather to "around 50 grandchildren".

Mirziyoyev's career trajectory is typical for a leader in post-Soviet Central Asia, where ex-Communist Party functionaries like Karimov have dominated political life since independence in 1991.

An engineer by training, Mirziyoyev rose to the position of head of the same academic institute he graduated from in Tashkent, and was elected to the country's last Soviet-era legislature in 1990.

Between 1996 and 2001 he served as governor of the agriculturally important region of Jizzakh, where he was born, before taking the governorship of Karimov's own home region of Samarkand.

During his 13 years as premier he was regularly touted as a potential successor to Karimov, along with current deputy prime minister Rustam Azimov and Karimov's eldest daughter Gulnara Karimova.

But the 44-year-old Karimova, a businesswoman and singer, has been reportedly under house arrest in the country since 2014 after publicly feuding with her mother and her younger sister Lola.

Neither the allegedly very corrupt Karimova, nor her two children attended the strongman's funeral.

Her eldest son Islam Karimov Jr, who lives in London, called on authorities to prove she was alive and well, in a recent interview with the BBC.

- Inching out of isolation? -

Under Karimov, Uzbekistan enjoyed mostly cordial relations with foreign powers active in the region but kept all of them at arm's length while regularly threatening smaller neighbours Kyrgyzstan and Tajikistan.

The country with the region's largest army exited a Moscow-led security bloc in 2012 and in 2005 ejected US forces from a military base used for Afghanistan operations following a bilateral spat.

Mirziyoyev was quick to meet with Putin after Karimov's death and last month hosted President Recep Tayyip Erdogan of Turkey, with whom Karimov enjoyed patchy relations.

"Under Karimov, Uzbekistan withdrew into itself, to its great cost, and this may be the main difference under Mirziyoyev," said analyst Rabbimov.

"He will see the country can't survive in isolation."