Kazakhstan warned Monday it could nationalise struggling energy companies in the oil-rich Central Asian country after the latest blackout there left thousands without electricity in freezing temperatures.

The vast ex-Soviet country is a net exporter of energy, but high gas prices this year fuelled historic and bloody protests, and ageing infrastructure leads to persistent electricity disruptions.

Thousands of people since Sunday are without heating in northern Kazakhstan with temperatures around -30 degrees Celsius (-22 Fahrenheit), after an accident at the power plant supplying the city of Ekibastuz.

"President Kassym-Jomart Tokayev has instructed Prime Minister Alikhan Smailov to study the issue of nationalising problematic energy assets," presidential spokesman Ruslan Zheldibay said on Facebook.

"Their mismanagement causes accidents and breakdowns in the supply of electricity," he said adding that those responsible for the accident in the city should be "brought to justice".

Kazakhstan gained independence from the Soviet Union in 1991 but it relies on an electricity system linked with four other ex-USSR Central Asian states.

Kazakhstan as well as neighbouring Kyrgyzstan and Uzbekistan suffered a huge blackout in January, ahead of the unrest.

Last month, Kazakh authorities said 65 percent of regional electricity networks needed repair.

Kazakhstan derives almost all its electricity from gas and coal but also imports some electricity to supply regions in the south.

Tokayev was re-elected this month winning 81 percent of votes, according to authorities but international election monitors said he faced no real competition.

Under former leader, authoritarian Nursultan Nazarbayev, in power for three decades, the energy sector was liberalised and passed into the hands of powerful oligarchs.