A Russia-led security alliance of ex-Soviet states will send peacekeeping forces to Kazakhstan, Armenia's prime minister said on Thursday, after the Kazakh president appealed for their help amid escalating unrest.

Armenian Prime Minister Nikol Pashinyan said on Facebook that an unspecified number of peacekeepers would go to Kazakhstan for a limited period to stabilize the situation, after government buildings were torched in the city Almaty and its international airport was seized.

Eight police and national guard troops were killed in the unrest on Tuesday and Wednesday, Russia's Sputnik agency quoted the Kazakh interior ministry as saying on Wednesday. Russian news agencies, quoting Kazakh media, later said two soldiers had also been killed in what they described as an anti-terrorist operation at Almaty airport.

The United Nations is following the unrest in Kazakhstan with concern, and calls for restraint, said a spokesman on Wednesday.

"We are obviously following with concern and are monitoring the situation in Kazakhstan. I think it's very important for all involved in these current events to exercise restraint, refrain from violence, and promote dialogue in addressing all of the pertinent issues," said Stephane Dujarric, spokesman for UN Secretary-General Antonio Guterres.

The protests began in the oil-producing western province of Mangystau on Sunday following the lifting of price caps on liquefied petroleum gas (LPG), a popular car fuel, causing consumer prices to surge. The demonstrations quickly spread to other parts of surrounding Mangystau Province and the country's largest city, Almaty.

Demonstrators took control of Almaty's international airport, a source familiar with the matter told Reuters. Flights were then canceled.

In the early hours of Thursday, in his second televised speech within hours, Tokayev said: "It is an undermining of the integrity of the state and most importantly it is an attack on our citizens who are asking me to help them urgently. 

"It is an undermining of the integrity of the state and most importantly it is an attack on our citizens who are asking me to help them urgently."

States of emergency were declared in Nur-Sultan, Almaty, and the western Mangystau Province, including an overnight curfew and a ban on mass gatherings. The internet was shut down. 

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Kazakh president vows to act tough in response to mass protests

On Wednesday, Tokayev signed a presidential decree to accept the resignation of the country's government.

The president then ordered acting ministers to reverse the fuel price rise, which doubled the cost of liquefied petroleum gas.

(With input from agencies)