CBI has registered a case in connection with alleged kidnapping of yoga exponent Ramdev's guru Swami Shankar Dev who mysteriously went missing six years ago while taking a morning walk in Haridwar.

CBI sources said a case under Section 365 of Indian Penal code against unknown persons. The section pertains to kidnapping or abducting and wrongful confinement. Uttarakhand Police registered a case of abduction to probe the disappearance of Dev, who had been living in Ramdev's ashram but was missing since July 2007 when he had gone out for a morning walk.

The FIR was reportedly filed by Ramdev’s aide Acharya Balkrishna at Kankhal police station three days after the Swami went missing under mysterious circumstances.

The state government had earlier sent a request to CBI in October last year to probe the case but the same was rejected as the state police had not even registered a case, the basic formality before the agency takes up the probe.

Swami Shankar Dev was the founder of Divya Yog Mandir Trust, currently headed by Ramdev who is under scanner for alleged violations in labelling of some of the products of the Trust.

Ramdev had earlier welcomed the decision of the government for a CBI probe into the disappearance of his guru.

Ramdev and his trusts are facing a number of probes by the Income Tax, Service Tax and Enforcement Directorate for alleged evasion of taxes and irregularities in complying with forex laws.