The White House and the United Nations on Wednesday urged Kazakh authorities to show "restraint" in dealing with violent civil unrest, as the government there declared a state of emergency after protests.

White House Press Secretary Jen Psaki said the United States supports "calls for calm" and said protesters should be able to "express themselves peacefully," urging the authorities "to exercise restraint."

The United Nations also called for all parties to "exercise restraint, refrain from violence and promote dialogue."

UN spokesman Stephane Dujarric said the international body was following events in the Central Asian country "with concern."

Kazakhstan on Wednesday declared a nationwide state of emergency after protests over a fuel price hike erupted into clashes and saw demonstrators storm government buildings.

Psaki said "crazy Russian claims" about a US hand behind the mass demonstrations are "absolutely false and clearly a part of the standard Russian disinformation playbook."

The country has been roiled by protests since the start of the year which escalated Wednesday into clashes with police.

Authorities cut internet and mobile phone access nationwide and earlier declared states of emergency in the epicentres of the rallies -- financial capital Almaty and the Mangystau province -- as well as in the capital Nur-Sultan, where no demonstrations have so far been reported.

The state of emergency was later extended across the entire ex-Soviet country.