Police in Kazakhstan killed "dozens" of protesters who tried to storm administrative buildings overnight in the country's biggest city Almaty, police told local media on Thursday.

"Last night, extremist forces tried to assault administrative buildings, the Almaty city police department, as well as local police commissariats," police spokesman Saltanat Azirbek was quoted as saying by Interfax-Kazakhstan, TASS and Ria Novosti news agencies.

"Dozens of assailants were eliminated," he said, adding that police were verifying their identities.

According to local media, the interior ministry said at least eight law enforcement officers have been killed and 317 wounded in the violence.

Long seen as one the most stable of Central Asia's ex-Soviet republics, energy-rich Kazakhstan is facing its biggest crisis in decades after protesters angry over rising fuel prices stormed government buildings.

A Russia-led military alliance said it would send peacekeeping forces to "stabilise" the country, blaming the mass protests on "outside interference".