Sarsenbaev's death has resulted in a number of political casualties in recent days.
The head of the national security service (KNB), Nartay Dutbaev, resigned on 22 February following the news that KNB agents were arrested for the killing.
And then, on 22 February, Erzhan Utembaev, the head of the Senate administration, was arrested for allegedly organizing Sarsenbaev's death.
In a statement released on 23 February, opposition leaders demand that Senate speaker Nartay Abykaev resign, saying he has enough power to influence the probe into Sarsenbaev's death.
Abykayev is also a former head of the KNB.
Opposition figures have accused government officials of playing a role in Sarsenbaev's murder.
Sarsenbaev, who was found shot dead on 13 February, was the co-chairman of the Naghyz Ak Zhol (True Bright Path) party.