* December unrest was a "warning", says Pillay
* Rights chief says growth can mask despair
* Foreign ministry says citizens' rights "fundamental value" (Adds Foreign Ministry comment)
By Raushan Nurshayeva
ASTANA, July 12 (Reuters) - The United Nations urged Kazakhstan on Thursday to allow an international investigation into deadly oil town riots that it said exposed rights abuses and growing inequality in Central Asia's largest economy.
U.N. High Commissioner for Human Rights Navi Pillay said the December riots in Zhanaozen, during which police opened fire on protesters, should serve as a "warning" to Kazakhstan not to pursue financial prosperity at the expense of human rights.
"Ignoring this was the mistake made in Tunisia, where very positive economic indicators masked the despair of a population deprived of many of their fundamental human rights," Pillay told a news conference during her first visit to Central Asia.
President Nursultan Nazarbayev has prioritised economic growth over democratic freedoms in more than two decades at the helm of Kazakhstan, a former Soviet state of 16.7 million people with 3 percent of the world's recoverable oil reserves.
Kazakhstan's economy, worth $185 billion at the end of last year, has expanded by an average 8 percent annually over the last decade. Foreign investment has exceeded $150 billion and per capita GDP is on par with that of Turkey or Mexico.
But the unrest in December shattered an image of stability. At least 15 people were killed in Zhanaozen and a nearby village, in the culmination of a seven-month labour dispute by oil workers in the western region of Mangistau.
"A precise account of exactly what happened in Zhanaozen, both during the tragic events themselves and afterwards, remains elusive," Pillay said.
"It is not clear who gave the orders allowing police to open fire, nor precisely why they did so," she said. Allegations of torture and forced confessions, she said, did not appear to have been properly investigated.
"I have recommended to the government that the only way to credibly answer these questions once and for all, and draw a line under these tragic events, is to authorise an independent international investigation into the events themselves, their causes and their aftermath," she said.
Kazakh Foreign Ministry spokesman Altai Abibullayev said the U.N. commissioner's evaluation of the Zhanaozen events was "one-sided", and the United Nations and other international bodies had already been invited to gather information.
"The right to life, the provision of security and basic social, economic and humanitarian rights for every citizen of Kazakhstan remain fundamental values for us," he said.
After a 10-week trial that ended last month, 34 people were convicted of rioting in Zhanaozen, although only 13 were sent to prison.
Separate trials led to the conviction of six policemen for abuse of power, including the head of a remand centre found guilty of failing to allow medical aid for a man who later died.
Prosecutor-General Askhat Daulbayev, who met Pillay earlier, said these trials had been conducted transparently and had been open to international observers and relatives of the accused.
Pillay said the events of Zhanaozen, if properly investigated, could become a "watershed" for Kazakhstan.
"It contains, in microcosm, many of the human rights concerns and critical gaps in the country's laws and rule-of-law institutions," she said. "These include allegations that torture is still practised in Kazakhstan."
The U.N. representative urged Kazakhstan to create an independent body with the power to inspect detention centres and to halt the common practice of failing to register people during their first few hours of detention.
In a statement posted on its website, www.prokuror.kz, the prosecutor-general's office quoted Daulbayev as saying international observers had visited remand centres in Zhanaozen and Aktau, and found no evidence of torture.
Pillay also said freedom of assembly was "far too restricted" and the root causes of the original labour dispute in Zhanaozen reflected wider social and economic problems, including huge differences in access to resources for urban and rural citizens. (Writing by Robin Paxton; Editing by Sophie Hares)