Deputy Commissioner of Police (Bengaluru West) M N Anucheth, the investigating officer in the case, said T Naveen Kumar alias Hotte Manja, already in judicial remand in connection with another case, was taken into custody for eight days.
The DCP, however, declined to divulge any further information.
Lankesh, 55, known as an anti-establishment voice with strident anti-right wing views, was shot dead at close range by unknown assailants at her home here on September 5 last year.
Police said Kumar was arrested on February 19 on charges of illegally possessing five bullets.
A case under the Arms Act was registered against him and he was remanded to judicial custody by a court.
Based on information provided by him earlier, police wanted to question him further and moved the court which yesterday granted eight days police custody.
Police sources said his looks matched with one of the sketches of the suspect and the photograph developed from a CCTV footage obtained from Lankesh's residence.
The killing of Lankesh drew widespread condemnation.
Photograph: PTI Photo