Some employees of KazMunaiGas Exploration Production are staying away from work because they fear for their safety after violent clashes killed at least 10 people in a western Kazakh oil city, the company said on Saturday.

London-listed KMG EP said Kazakhstan's Interior Ministry was providing armed security at key oil production facilities after the clashes on Friday, when a crowd set fire to the headquarters of its Uzenmunaigas unit in the city of Zhanaozen.

The company said in a statement it was maintaining daily oil production levels by keeping employees working round the clock.

Some Uzenmunaigas workers failed to appear for the night shift and the morning shift on December 16 and 17, KMG EP said.

This can be explained by the fact workers are afraid for their own security and the security of their family members.

Public protests are scarce in Kazakhstan, Central Asia's largest economy and oil producer, where President Nursultan Nazarbayev has ruled with a firm hand for more than 20 years and has overseen massive foreign investment, mainly in oil and gas.

The unusually violent clashes in Zhanaozen, a city of 90,000 people about 150 km inland from the Caspian Sea, marred celebrations to mark the 20th anniversary of Kazakhstan's independence from the Soviet Union.

Sacked oil workers clashed with riot police in the city's central square. Ten people were killed and buildings and cars were set on fire, Prosecutor-General Askhat Daulbayev said.

Some KazMunaiGas EP workers began a months-long strike in May, demanding better pay and conditions. The company, which said the strikes were illegal, sacked 989 workers but sporadic protests have been held in the town since the strike ended.

New York-based Human Rights Watch said at least some mobile phone and Internet access had been shut down in Zhanaozen and called on the Kazakh government to observe human rights norms as they restore order.

Without a means of communication with the outside world, people in Zhanaozen are extremely vulnerable, said Mihra Rittmann, Central Asia researcher at Human Rights Watch.

Even in times of unrest and violence, when police restore order they should do so without using excessive force, she said in a statement.

The rights body also said around 100 people were detained and later released after a peaceful rally in the regional centre of Aktau, a larger city on the Caspian coast.

Daulbayev, the prosecutor-general, said investigators led by the interior minister had travelled to Zhanaozen on the orders of the president to take all necessary measures to preclude further criminal acts, identify and punish organisers of the disorder and restore public security in the town.

(Additional reporting by Mariya Gordeyeva and Dmitry Solovyov; editing by Tim Pearce)