The same group of right-wing activists is behind the killings of rationalists Narendra Dabholkar, M M Kalburgi and journalist Gauri Lankesh, a senior police official said quoting investigation reports.
However, the probe agencies have not been able to establish the group's link with the killing of rationalist and communist leader Govind Pansare, he said.
"During the investigation, it came to light that a gang of like-minded people was involved in the killings of Dabholkar, Lankesh and Kalburgi. Almost all members of this gang have links with the Sanatan Sanstha and its offshoot Hindu Janjagruti Samiti," the official said Saturday.
Dabholkar, Kalburgi and Lankesh were assassinated by members of this gang because they were raising their voice against the Hindu religion, he claimed.
"The probe so far indicates that those arrested in connection with the seizure of huge cache of explosives from Nallasopara in Palghar district have direct links with the killings of Dabholkar, Kalburgi and Lankesh," he said.
Meanwhile, efforts are on to nab those behind Pansare's killing, the official said.
The Maharashtra Special Investigation Team (SIT) is probing Pansare's killing.
While Dabholkar was shot dead in Pune in August 2013, Pansare was shot at on February 16, 2015 in Kolhapur and succumbed to his injuries on February 20.
Lankesh was killed at her house in Bengaluru in September last year while Kalburgi was shot dead at the entrance of his house in Karnataka's Dharwad district on August 30, 2015.
After the seizure of explosives from Nallasopara last month, the Maharashtra Police has arrested at least 10 people and said it will investigate their role in all detected and undetected cases, including the killings of Dabholkar, Pansare, Kalburgi and Lankesh.
During the interrogation, one of the arrested persons, Sharad Kalaskar, admitted to his involvement in Dabholkar's killing, police had said.
On his information, the Maharashtra Anti-Terrorism Squad (ATS) and the Central Bureau of Investigation (CBI), which is investigating Dabholkar's killing, arrested Sachin Andure from Aurangabad.
Kalaskar and Andure allegedly shot dead Dabholkar with two pistols in Pune, the official said.
The CBI had earlier arrested Virendrasing Tawade, the alleged 'mastermind' of the killing.
"During our investigation, it came to light that Tawade played a major role in the planning and execution of the three assassinations (Dabholkar, Lankesh and Kalburgi)," the official claimed.
While investigating Lankesh's killing, the Karantaka Special Investigation Team (SIT) arrested Pune-based engineer Amol Kale, who had names and mobile numbers of the other group members in his diary, including Vaibhav Raut, Sudhanva Gondhalekar, Sharad Kalaskar and others, the official said.
Kalaskar had travelled to Karnataka to do a recce of Lankesh's residence, he said.
As part of further probe, the Maharashtra ATS Wednesday obtained the custody of Bharat Kurne and Sujeet Kumar, who were originally arrested by the Karnataka SIT in Lankesh's killing case, in connection with the seizure of explosives from different parts of the state.
Names of Kurne and Kumar surfaced while going through the documents, diaries and data stored in a computer which was seized during raids by the ATS at various places, including Nallasopara, Pune and Aurangabad, the official said.
Sujeet Kumar alias Praveen is also wanted in connection with Kalburgi's killing. During the Karnataka SIT's investigation, it came to light that Kumar allegedly shot Kalburgi.
Kurne and Kumar were allegedly involved in the training of handling of arms and explosives along with those arrested by the Maharashtra Police in the explosives' seizure case, the official said.
Kurne, a resort owner in Karnataka's Belgaum district, had provided shelter to those accused in Lankesh's killing. His three acre farmland at Khanapur forest was also used for fire arm training sessions, he added.