Kazakh president Nursultan Nazarbayev has extended a state of emergency in the western oil city of Zhanaozen until the end of January.
At least 16 people were killed in the city last month in the nation's deadliest clashes in decades.
Mr Nazarbayev imposed a 20-day state of emergency and curfew in the city in December 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 December 16th dealt a blow to the image of stability touted by Mr Nazarbayev as his main achievement in the vast nation of 16.6 million, Central Asia's largest economy and oil producer.
The violence in Zhanaozen, 150km (95 miles) from the Caspian Sea, was followed by a riot in the nearby village of Shetpe on December 17th, where another person was killed.
More than 100 people were wounded in the clashes. Last week Mr Nazarbayev sacked his billionaire son-in-law Timur Kulibayev, one of the country's richest and most influential people, as head of sovereign wealth fund Samruk-Kazyna, which manages state assets worth around $90 billion.
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.
Mr Nazarbayev, a 71-year-old former steelworker who has put market reforms in place and overseen foreign investment but brooks no dissent, is under international pressure to investigate the violence.
His decree, published on the presidential website www.akorda.kz, 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.
Kazakhstan holds an early parliamentary election on Jan. 15 in which Nazarbayev's ruling Nur Otan party is widely expected to win a majority of seats.
Last week, Mr Nazarbayev forbade all government and local officials from leaving the country for holidays, saying they needed "to be closer to people and to keep fingers on the pulse" in the run-up to the polls.
The United States and the European Union have expressed concern about the violence in western Kazakhstan and urged authorities to conduct a transparent investigation.
Kazakh officials have said they have invited United Nations experts to join an investigation.