In a confessional statement under Section 164 of the CrPC before a court in Gaibandha he admitted being the mastermind of the killing, Additional DIG of Rangpur Range Police Ahmed Bashir told bdnews24.com.
Senior Judicial Magistrate Jainal Abedin recorded the statement from 3pm to 9pm on Saturday, he said.
Kader Khan is a retired medical doctor from Bangladesh Army.
Police arrested him from his residence in Bogra town on Tuesday last week on charges of killing MP Liton who was shot at his Sundarganj residence on Jan 31.
Police say Kader was tempted to become an MP again from Gaibandha-1 (Sundarganj) constituency that motivated him to plan the killing of the sitting MP.
Kader Khan collected nomination paper to contest in the by-election for the vacant seat but did not submit the nomination paper. The election will be held on Mar 22.
He was elected MP as a Grand Alliance candidate from Jatiya Party in 2008 from the same constituency Liton was representing.