The decision to despatch peacekeepers was a first for the Moscow-led Collective Security Treaty Organisation (CSTO), often touted by Russia as a NATO equivalent but previously reluctant to interfere in unrest in Central Asia -- a region with long historical ties to Russia.

Russia's defence ministry said the "collective peacekeeping forces ... are starting to prepare equipment and materiel for loading into the planes of the military transport aviation of the Russian aerospace forces and returning to the points of permanent deployment."

Kazakh President Kassym-Jomart Tokayev framed the clashes as a coup attempt assisted by local and international terrorists.

Russian counterpart Vladimir Putin hinted that the violence was reminiscent of "colour revolutions" instigated by foreign meddling.

Tokayev has said the phased withdrawal of the foreign troops would take no more than 10 days.

Concern had mounted that Moscow could leverage the mission to shore up its influence in Kazakhstan.

US Secretary of State Antony Blinken earlier warned that "once Russians are in your house, it's sometimes very difficult to get them to leave".

While authorities have described the violence as the work of foreign "terrorists", it erupted on the back of peaceful demonstrations over a rise in fuel prices and against a background of deteriorating living standards and endemic corruption.