Kazakhstan has extended until 31 January a state of emergency in the western oil city of Zhanaozen.

Sixteen people were killed last month in Zhanaozen in the nation's deadliest clashes in decades.

On 17 December, President Nursultan Nazarbayev imposed a 20-day state of emergency and curfew in the city after a seven-month strike by oil workers over wages and sackings erupted into clashes with police.

The state of emergency had been due to be lifted tomorrow.

The bloodshed, on Independence Day on 16 December, dealt a blow to the image of stability touted by Mr Nazarbayev as his main achievement in the nation of 16.6m.

Kazakhstan is Central Asia's largest economy and oil producer.

The violence in Zhanaozen, 150km from the Caspian Sea, was followed by a riot in the nearby village of Shetp, where another person was killed.

More than 100 people were wounded in the clashes.

Last week the president sacked his billionaire son-in-law Timur Kulibayev, one of the country's most influential people, as head of sovereign wealth fund Samruk-Kazyna, which manages state assets worth around $90bn (€69bn).

Mr Nazarbayev had earlier fired the heads of state oil company KazMunaiGas and its London-listed production unit, accusing the management of failing to obey his order to resolve a labour dispute that had been simmering since May.

The president - a 71-year-old former steelworker - is under international pressure to investigate the violence.

His decree gave no reason for the extension of the state of emergency, which bans strikes and public protests, restricts freedom of movement around Zhanaozen and limits access to and from the city.

The US and the EU have expressed concern about the violence in western Kazakhstan and urged authorities to conduct a transparent investigation.

Kazakh officials have said they have invited UN experts to join an investigation.