External military assistance to Kazakhstan brings back "memories of situations to be avoided," the European Union’s foreign policy chief said Thursday. 

Expressing the EU's "great concern" over developments in Kazakhstan, where people have been protesting against rising fuel prices, Josep Borrell said on Twitter that the rights and security of civilians must be guaranteed.

"The EU is ready to support in addressing this crisis," he added.

The Collective Security Treaty Organization (CSTO), a Russia-led military alliance, sent peacekeeping troops earlier in the day to Kazakhstan, where massive riots stemming from nationwide protests over high fuel prices have led to a state of emergency and the resignation of the government.

The protests began in western Kazakhstan on Jan. 2 over an increase in the prices of liquefied petroleum gas (LPG) and later spread to other areas of the country before going nationwide.

A state of emergency was declared in the commercial capital Almaty and the oil-rich Mangystau region to ensure public safety.

On Wednesday, Kazakh President Kassym-Jomart Tokayev approved the resignation of the government.

He also requested help from CSTO -- the forces of which consist of military units from Russia, Belarus, Armenia, Tajikistan and Kyrgyzstan -- which agreed to send an unspecified number of peacekeepers. The peacekeeping forces were sent on Russian Air Force planes.