* Opponent of Kazakh leader jailed for seven-and-a-half years
* U.S. says criminal system used to silence opposition voices
* Kazakhstan says trial of Vladimir Kozlov fair and open By Robin Paxton
ALMATY, Oct 9 (Reuters) - The United States on Tuesday accused Kazakhstan of using its justice system to "silence opposition voices" after a prominent critic of President Nursultan Nazarbayev was jailed for inciting violence.
Vladimir Kozlov was found guilty on Monday of colluding with a fugitive billionaire in a failed attempt to rally oil workers to bring down the government of the Central Asian state.
Kozlov, 52, was sentenced to seven-and-a-half years in prison and had his property confiscated. He has called his case an "undisguised attempt" to stifle protest and labour rights.
"We note our concern regarding the prosecution of Vladimir Kozlov and the apparent use of the criminal system to silence opposition voices," the U.S. Embassy said in a statement.
The criticism will hit home in Kazakhstan, which is a strategic ally of the United States in former Soviet Central Asia, a resource-rich region to the north of Afghanistan where Russia and China also vie for influence.
In more than two decades as president, Nazarbayev, 72, has eschewed democratic freedoms in pursuit of the oil-fuelled growth and investment that has made Kazakhstan's $185 billion economy the largest in Central Asia.
Authorities have tried in recent years to balance their desire to preserve stability with efforts to improve Kazakhstan's image on the world stage. The country chaired the Organisation for Security and Cooperation in Europe in 2010.
Kozlov was charged with orchestrating dissent among striking oil workers in the prelude to riots last December that killed 15 people. Two opposition activists tried alongside him were freed on suspended sentences.
Judge Berdybek Myrzabekov said Kozlov had politicised a labour dispute under orders from Mukhtar Ablyazov, an arch foe of Nazarbayev and the self-exiled former head of BTA bank.
Kazakhstan's Foreign Ministry said the trial had been fair and open to everyone.
"I disagree strongly with the politically motivated insinuations about the alleged lack of a fair and impartial judgment," said Altay Abibullayev, spokesman for the ministry.
'PAYING THE PRICE'
Kazakhstan's marginalised opposition enjoys little support at home. Despite never having held an election judged fair by Western monitors, Nazarbayev is popular in the country of 17 million for presiding over stability relative to its neighbours.
But authorities have grown more wary of dissent after street protests in Russia, which shares a language with millions of Kazakhstan's citizens and remains the country's biggest trade partner.
"The hearing sends a clear message ... that any political activism which tries to channel social discontent into a political force against government, especially on the streets, is unwelcome," said IHS Global Insight analyst Lilit Gevorgyan.
Kozlov's Alga! party, long denied official registration, was ineligible to stand in a parliamentary election in January. The confiscation of his assets, including a dozen Alga! offices registered in his name, is a serious blow to the organisation.
"Kozlov is paying a heavy price for publicly criticising the Kazakh government," said Mihra Rittmann, Europe and Central Asia researcher at Human Rights Watch, which also said the trial fell short of international standards.
(Additional reporting by Raushan Nurshayeva in Astana)
Keywords: KAZAKHSTAN TRIAL/