By Mariya Gordeyeva
AKTAU, Kazakhstan (Reuters) - An outspoken critic of Kazakh President Nursultan Nazarbayev went on trial on Thursday charged with attempting to overthrow the government, in a case the United States says will test the oil-producing former Soviet state's democratic progress.
Vladimir Kozlov, leader of the unregistered Alga! party, is accused of helping orchestrate dissent among oil workers in a region where deadly rioting on December 16-17 shattered Kazakhstan's reputation for stability.
He denies the charges and, as his trial began in a packed courtroom, his supporters called for his release.
At least 15 people were killed in the town of Zhanaozen and a nearby village when police opened fire on protesters, unrest that followed months of protests by sacked oilmen and posed the most serious challenge to Nazarbayev in his more than two decades in charge of the Central Asian republic.
Kazakhstan's leaders are particularly wary of dissent following mass protests in Russia, the country's biggest trading partner and a key cultural reference point for its millions of Russian-speaking citizens.
In recent years, they have tried to balance their desire to preserve stability with efforts to improve the country's image on the world stage.
Kozlov, 52, faces a maximum prison term of 13 years if convicted of charges that include inciting social unrest and trying to overthrow the constitutional order. Two independent opposition activists are on trial alongside him.
Dressed in an open-necked shirt, Kozlov waved at around 30 of his supporters when led into court in the Caspian port city of Aktau, 2,600 km (1,625 miles) west of the capital, Astana.
He asked the judge to postpone the hearing to allow him more time to familiarize himself with the 1,300-page case document. Permission was denied, prompting slow claps from his supporters that drew a warning from the judge.
"We have a feeling the trial will be rushed. I fear the verdict might already have been written and that the trial will be a formality," Mikhail Sizov, Kozlov's deputy in the Alga! party, said by telephone two days before proceedings began.
The country's marginalized and fragmented opposition enjoys relatively little popular support. Several hundred people attended a series of rallies held monthly in Almaty, the country's largest city, after a January 15 parliamentary election.
Nazarbayev, a former steel worker who rose through the ranks of the Soviet Communist party, remains popular across the mainly Muslim country of 16.7 million people and is credited for sustained economic growth in an otherwise volatile region.
Robert Blake, U.S. Assistant Secretary of State for South and Central Asia, said Kazakhstan had a "particular responsibility" to demonstrate reforms pledged as chair of the Organisation for Security and Cooperation in Europe in 2010.
"We hope that (the trial) is going to be conducted in a fair, impartial and open way," Blake told reporters in Almaty on the eve of the trial.
"We also hope that the trial itself will not undermine some of the progress that Kazakhstan is making to develop a multi-party democracy," he added.
The January election allowed three parties into Kazakhstan's parliament for the first time in 20 years of independence, a small concession to democracy in the face of growing frustration over the unequal distribution of the country's mineral wealth.
But the second- and third-placed parties are broadly sympathetic to Nazarbayev's ruling Nur Otan party, which itself won 81 percent of the vote. The OSCE's observer mission said genuine opposition parties had been barred and media shackled.
Kozlov's Alga! party, long denied official registration, was not eligible to run. He was arrested several days after the election. Prominent rights activist Yevgeny Zhovtis, observing the trial, said he expected a verdict by the end of August.
Earlier trials of people accused of participating in the December violence saw 23 people jailed.
(Additional reporting and writing by Robin Paxton in Almaty; Editing by Andrew Osborn)