Dutbaev offered his resignation after the KNB said on 21 February that five members of its elite Arystan combat unit have been arrested over the murder of opposition leader Altynbek Sarsenbaev.
The co-chairmain of the Naghyz Ak Zhol (True Bright Path) party was found shot to death, along with his bodyguard and a driver, on the outskirts of Almaty on 13 February.
Opposition figures suspect the authorities had a role in the killing. The Kazakh government denies this.
(RFE/RL's Kazakh Service)