Former Karnataka minister Vinay Kulkarni had travelled to Delhi before and after the killing of BJP worker Yogesh Gowda in Dharwad on June 15, 2016, to use it as an alibi, the CBI has alleged.
The Central Bureau of Investigation (CBI) had arrested Kulkarni, a Congress leader, on Thursday.
The CBI probe into the killing, so far, shows that Kulkarni, who was sent to judicial custody on Monday by a special court, had left for Delhi on June 12, 2016, at 11.30 am by a flight and returned the next day at 10.40 am.
Similarly, he allegedly left for Delhi on June 16, 2016, evening, a day after the murder, and returned on June 18, 2016, according to the probe by the CBI, which took over the investigation into the case on the recommendation of the Karnataka government.
"The tickets were booked on the same day of the journey and the purpose of the journey was to create an alibi," the CBI has alleged.
Gowda, a BJP Zilla Panchayat member, was killed in his gym in Dharwad by unidentified men on June 15, 2016, officials said.
Gowda's murder was a result of political rivalry as Kulkarni, the then MLA and minister, had allegedly asked him not contest the Zilla Panchayat elections, which the former had refused, according to the agency's probe.
Kulkarni and Gowda had entered into verbal altercations on several occasions, and a "serious altercation" took place during a Zilla Panchayat meeting chaired by Kulkarni on April 22, 2016, the CBI has alleged.
The agency has also alleged that the altercation triggered the conspiracy to murder Gowda.
The Congress has denied the allegations against Kulkarni and has called the case a political witch hunt.
"Congress leader Vinay Kulkarni's arrest by the 'puppet CBI' reflects the blatant conspiracy & malicious intent of CM, Yediyurappa & BJP leadership," Congress chief spokesperson Randeep Singh Surjewala tweeted.
B S Yediyurappa should know that Congress leaders will not be cowed down by such cowardly attacks of the BJP and its pawn, the CBI, he said.
Surjewala accused the Centre of "misusing " central agencies to "hound" Congress leaders.
He had also tweeted that a "fledgling" Yediyurappa government and the BJP "misuse its frontal organisations, the CBI-ED-Income Tax to hound Congress leaders- Sh. D.K.Shivakumar, Sh. G.Parameshwara, Sh. Vinay Kulkarni & many others".
The CBI has alleged that as part of the conspiracy, Kulkarni had intervened and assisted to broker a real-estate agreement between Basavaraj Muttagi, an accused in the case and Nagendra Todkar on May 24, 2016, less than a month before the killing.
The local police had shown the deal to be a purported property dispute between Muttagi and Gowda, and termed it as motive for murder in its charge sheet.
During the CBI probe, the owner of the property allegedly denied having any dispute with Gowda and also deposed before the trial court.
The agency has alleged that the killers, who had come from Bengaluru, were made to stay at a resort owned by a close confidante of Kulkarni on June 7, 2016, during first attempt to murder, the officials said.
The CBI has also alleged that Kulkarni had booked a room at a Bengaluru hotel between June 8 to June 20 and also met Muttagi a day after the murder at 01.30 am on June 16, 2016.