Kazakhstan President Kassym-Jomart Tokayev said Monday that militants from Central Asia, Afghanistan and the Middle East were behind historic violence that hit the country last week, the presidency reported.

The Central Asian country is reeling in the wake of the worst violence in its recent history, as the nation on Monday observed a day of mourning for dozens killed in the clashes.

"I have no doubt that it was a terror attack," Tokayev told European Council President Charles Michel by phone, his office said. 

Tokayev said the attack was "well organised" and involved "foreign fighters" from Central Asian countries, Afghanistan and the Middle East.

He accused the militants of seeking to create a "zone of controlled chaos" in order to seize power.

Separately, Russian Foreign Minister Sergei Lavrov and his Chinese counterpart Wang Yi also discussed the situation in Kazakhstan and voiced their "firm support" for efforts by the Kazakh authorities to restore order, Moscow said.

Both ministers "stressed their concern about the intervention of external forces, including the participation of foreign mercenaries in attacks on civilians and law enforcement officials, the seizure of state institutions and other facilities," the Russian foreign ministry said in a statement.

Both Kazakhstan's authoritarian government and Moscow have repeatedly blamed the unrest on forces outside the country, without offering evidence.

During the talks with Michel, Tokayev also said that economic damage could total $2-3 billion, citing preliminary estimates.

Following a request from Tokayev, the Moscow-led Collective Security Treaty Organisation (CSTO) has deployed troops and military hardware.

Tokayev told Michel that CSTO troops were in Kazakhstan only to protect strategic facilities. "They will remain in Kazakhstan until the situation fully stabilises," Tokayev added.

Kazakh authorities have until now struggled to provide a clear and full picture of the unrest.

On Sunday, the information ministry retracted a statement that said more than 164 people had died in the unrest, blaming the publication on a "technical mistake".