* Clashes, protests threaten Nazarbayev's authority
* Pressure mounts for change in ex-Soviet republic
* Nazarbayev has long ruled with an iron grip
By Dmitry Solovyov and Mariya Gordeyeva
ALMATY, Dec 19 (Reuters) - Riots by oil workers in western Kazakhstan suggest pressure is mounting for President Nursultan Nazarbayev to relax the rigid authoritarian system he has built in the vast Central Asian state, which is fast losing its veneer of stability.
Officials say 14 people were killed in Friday's clashes following the dismissal of oil workers in Zhanaozen in western Kazakhstan and another person was killed when violence spread to a nearby village on Saturday. It was a local crisis that had long been simmering and local authorities had failed to master.
"People want to be heard, but there are no mechanisms which would allow people to be heard...This results in such brutal methods," Kazakh political analyst Aidos Sarym said. "Zhanaozen actually threatened the unity of our nation."
"In general, there is a need to slacken the reins. Public mechanisms are needed. There are things which should be discussed in parliament," he said. "There must be modernisation of society, of the political system."
Nazarbayev, a 71-year-old former steelworker, has ruled the oil-producing steppe nation since Soviet times and overseen rapid market reforms crowned with fast economic growth and more than $120 billion in foreign direct investment.
But there is a huge discrepancy between the liberal economic model and the one-man political system under which Nazarbayev has sweeping powers, brooks no dissent and leads the ruling Nur Otan party in the former Soviet republic of 16.6 million.
Popularly known as "Papa", Nazarbayev has ruled the world's ninth largest country with an iron fist, ignoring criticism at home and abroad after crackdowns on independent media and dissidents.
He called early parliamentary elections in January that will install at least a nominal opposition presence in what is now a one-party chamber. But he has turned a deaf ear to Western calls to respect broader commitments he has made to democracy.
Nazarbayev remains popular in Kazakhstan, which has seen much instability in neighbouring states such as Kyrgyzstan and Tajikistan.
He was shown on state television moving from one celebratory gala to another in his futuristic new capital Astana as clashes were breaking out on the 20th anniversary of independence from the Soviet Union.
In the clashes, oil workers and their supporters confronted police and torched numerous official and private buildings in Zhanaozen. They were the deadliest clashes since Soviet times.
Thousands of oilmen had been on strike in the Mangistau region since May, demanding a rise in wages. About 2,000 striking workers were fired and the state machinery largely ignored the oil workers' complaints.
"It is a formidable challenge that has been thrown down to Nazarbayev," said Alexei Malashenko, an expert at the Carnegie Moscow Centre think tank.
"He simply slept through it, missed the blow ... and afterwards a disproportionate reaction followed."
"The protests also exposed the main weakness of the political system that Nazarbayev has crafted in 20 years of his rule -- it works as long as the leader is strong and relatively young," Lilit Gevorgyan, analyst at His Global Insight.
"At the time of transition, all the achievements born out of political and economic stability can be wiped away if political turmoil follows."
The Kazakh authorities have sought to shift blame away from Nazarbayev.
Yermukhamet Yertysbayev, a close adviser to the president, said foreign funding had fuelled the riots, but declined to elaborate. He said the situation was firmly under control.
"There will be no Arab-style revolution. You can see that Kazakhstan is calm," he said. "Kazakhstan's entire multi-national population supports the head of state."
Asked about a rally on Sunday in the city of Aktau, capital of the Mangistau region, he said: "You know, there are also rallies in New York and Cairo ... Citizens have the right to protest, so let's not draw global conclusions."
Amirzhan Kosanov, a Kazakh opposition leader, dismissed any suggestion of foreign involvement.
"I am afraid that these allegations about foreign provocateurs...will become a reason for the authorities to refuse to analyse the true causes of the events in Zhanaozen," Kosanov wrote on his Facebook page.
In addition to the dead, about 100 people were wounded in the clashes and a state of emergency has been declared in Zhanaozen.
The authorities blamed the bloodshed, arson and looting on "hooligans and oilmen who joined them". They imposed a curfew in Zhanaozen and now control all movement in and out of the city, although they say the situation has generally calmed down.
But in Aktau, hundreds of oilmen held a third day of rallies on Monday, facing lines of riot police, many with automatic rifles.
In almost every speech, Nazarbayev draws attention to living standards in Kazakhstan, which are much higher than in other Central Asian countries.
He also underlines "stability and harmony" in the mainly Muslim but multi-ethnic country as the main achievement of his rule.
But a series of explosions and shootouts across the country this year have unnerved the authorities, who originally blamed them on Islamist militants, but now routinely refer to unidentified "terrorists".
"The exemplary political stability which Nazarbayev has touted and presented as one of his biggest achievements shows growing cracks which come at the worst time for Nazarbayev," Gevorgyan said.
"The symbolism could not have been better - as he was celebrating his achievements, the events in western Kazakhstan came to show the reality. Kazakhstan is not as stable as Nazarbayev or his government would like to show to foreign investors."
Analyst Malashenko said he believed that "Nazarbayev is in a very precarious situation. I think he has been losing so far, and should he suppress the current outbursts with force, something similar is likely to erupt."
News of the suppression of the riots has spread on social network sites, as has happened during recent protests in Russia against alleged election fraud and in the Arab world.
The picture has been different in the traditional media in a throwback to Soviet times, when Nazarbayev was a Communist Party boss.
The main state channel, Khabar, ran a feature film about Nazarbayev's life and interviews with him. Singers sang songs with lyrics written by him, and video clips lionised him as "the founder of new Kazakhstan".
Internet, mobile communication and telephone landlines were cut off from Zhanaozen. Communication has been patchy elsewhere across the sprawling nation.
"This manner of behaviour -- by blocking social networks and jamming information -- has shown to the entire world that the authorities have actually lost," Malashenko said. (Additional reporting by Robin Paxton; Reporting by Dmitry Solovyov)