"Peacekeeping forces of the Collective Security Treaty Organisation were sent to the Republic of Kazakhstan for a limited time to stabilise and normalise the situation," the CSTO secretariat said in a statement posted by Russian foreign ministry spokeswoman Maria Zakharova.

It said the deployment included units of the armed forces of Russia, Belarus, Armenia, Tajikistan and Kyrgyzstan, the five other members with Kazakhstan of the Moscow-dominated CSTO.

The statement did not specify how many troops were being sent but said the Russian contingent included members of the country's Airborne Forces.

The troops' main tasks "will be the protection of important state and military facilities and assistance to the forces of law and order... in stabilising the situation," the statement said.

It said Russian forces were being transferred by military aircraft to Kazakhstan and that advance units had "already begun to fulfil the assigned tasks."