A senior official in the Special Investigation Team also said the same weapon was used to shoot Ms Lankesh, and rationalists Govind Pansare and M M Kalburgi. "Waghmare shot Lankesh and the forensic report has confirmed that (rationalists) Govind Pansare, M M Kalburgi and Lankesh were murdered with the same weapon," a senior officer in the SIT told PTI wishing not to be named.
He, however, said the weapon was yet to be traced.
Forensic examination can lead to such a conclusion when the hammer of a gun has left identical marks at the rear of a bullet even if the weapon itself has not been found.
The official said the organisation, composed of people drawn from Hindu right groups, had around 60 members spread across at least five states but had no name. "We discovered that this gang has a network in Madhya Pradesh, Gujarat, Maharashtra, Goa and Karnataka. We did not find their Uttar Pradesh connection so far," the official said.
Hindutva organisations like Maharashtra-based Hindu Jagruti Samiti and Sanatan Sanstha, these outfits may not be directly responsible for the killings.
Both organisations had denied their role in the killing of the three.
Sujith Kumar alias Praveen used to recruit people for the gang, the official said, adding it was following his interrogation that the network was busted.
The SIT, he said, suspected three more were involved in the killing of Lankesh, who was shot dead at the entrance of her Bengaluru residence on September 5 last year, and a hunt was on for them.
Speculation was rife that Parashuram Waghmare, whose physical appearance matched that of the man whose image was caught on the CCTV camera at Ms Lankesh's home on the day of the killing, was her assassin.
"The gang had almost reached the last phase of killing Prof K S Bhagawan (Kannada writer) when we nabbed them," the officer said.
The Karnataka police had uncovered the plot to kill Mr Bhagwan recently, and it was during the interrogation of the four arrested accused that they grew suspicious about their involvement in Gauri Lankesh's killing.
Mr Bhagwan had often angered the right-wing outfits with his writing and utterances against Hindu Gods.
The SIT had recently recovered a diary from the suspects which contained a hit list of targets. The name of film and theatre personality Girish Karnad figured in the list, the officer said, adding the Jnanpith awardee's surveillance was in the "last phase".
Other than Mr Bhagvan and Girish Karnad, former minister and literatteur B TLalitha Naik, rationalist C S Dwarakanath and pontiffVeerabhadra Channamalla Swamy of Nidumamidi Mutt were also onthe hit list. All of them have been quite vocal in criticising the Hindu right.
Kalburgi, a Sahitya Akademi Award winner and a doughty campaigner against superstition in Hinduism, was shot dead in August 2015 at his home in Karnataka's Dharwad district.
In February the same year, Govind Pansare, a Left politician and rationalist, was shot at and fatally injured by unidentified assailants in Kolhapur in Maharashtra.