The BJP has blamed the Trinamool Congress, which has rubbished the allegation.
The body of a BJP worker was found inside the party office at Usthi in West Bengal's South 24 Parganas district, a police officer said on Saturday.
The worker, Prithviraj Naskar, used to handle the social media accounts of the party in the district.
The BJP pointed an accusing finger at the Trinamool Congress (TMC), while the police, after arresting a woman in connection with the killing, said the reason for the murder could be personal.
Naskar's blood-soaked body was discovered at the party office on Friday night. His family members said he had been missing since November 5.
A senior police officer said the arrested woman confessed to having hit Naskar with sharp weapons, resulting in his death.
"We are exploring the angle of the deceased having been involved in a relationship and any quarrel with the arrested person," he told reporters.
The officer said a police team broke open the front door and a collapsible gate locked from inside of the party office before finding the body. The suspected assailant must have escaped through a rear door.
Following a preliminary investigation and tracking of mobile phones, the woman was picked up from a nearby locality and, during interrogation, she confessed that she had committed the crime, the officer said.
Police are investigating if she was aided and abetted by anyone else, he said.
The BJP accused the ruling TMC and the party hit back.
BJP State President Sukanta Majumdar told reporters that local TMC activists were behind Naskar's murder as they wanted to frighten the party's supporters in the area.
In a post on X, Mr Majumdar said, “Our fight will continue until justice is served and the killers of martyr Prithviraj are brought to light. BJP remains resolute in ending the bloodthirsty and oppressive rule of CM Mamata Banerjee in Bengal.”
The BJP state unit alleged in another X post that the party's district social media convenor was abducted, tortured and murdered by TMC "goons".
“The police ignored his family's desperate pleas for help,” it claimed.
Senior TMC leader and former Rajya Sabha MP Kunal Ghosh claimed that the BJP knows the exact reason behind Naskar's death but peddles falsehoods implicating the TMC.
Mr Ghosh claimed in an X post that there are reports about the BJP worker having enmity with more than one person.
The injuries in some parts of his body showed animosity and contempt of the assailant towards the man, the TMC leader claimed, expressing hope that the investigation would cover all these angles.
Meanwhile, Naskar's father claimed that his son had earned the wrath of some local TMC activists and the police after putting up placards demanding justice for the RG Kar hospital victim during the recent Durga Puja festival in the area.
"My son was warned of dire consequences by local TMC leaders for organising protests on the RG Kar issue during the festive season," the father said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)