In Bishkek, the capital, more than 100 protesters rallied in front of the parliament building with the same demand.
Keldibekov, a member of the opposition Ata-Jurt (Fatherland) party, served as parliament speaker between 2010 and 2011. He was detained on November 20 amid an investigation into alleged abuse of office and financial misdeeds while running the State Social Fund and Tax Service several years ago.
In a video statement placed on the Internet hours before his detention, Keldibekov called the case against him politically motivated.
Several lawmakers met with the protesters in Bishkek, saying that the prosecutor-general will report on Keldibekov's arrest in parliament later on November 21.