Raj Singh, arrested in Balia by a Bengal Special Investigation Team (SIT) in connection with the killing of Chandranath Rath, aide to Bengal Chief Minister Suvendu Adhikari, returned home on Thursday after being cleared by the CBI and Barasat court in Bengal.

The CBI had petitioned the Barasat court for Singh's release, saying he had been arrested in a case of mistaken identity. The agency, which assumed control of the investigation from the SIT, arrested the "real" Raj Kumar Singh in Muzaffarnagar, Uttar Pradesh, on May 18.

Acting on the CBI's plea, the Barasat court in Bengal ordered Raj Singh's release. He returned to his home in Ballia on Thursday.

Chandranath Rath, Adhikari's personal assistant, was shot dead in Madhyamgram on May 6, two days after the declaration of the fiercely fought Bengal Assembly election results.

The CBI took over the investigation into Rath's murder from the Bengal Police following a request from the state government.

Officials said the agency had constituted a seven-member special investigation team, led by a deputy inspector general from its Special Crime unit in Delhi and comprising investigators drawn from several divisions.

After returning home, Singh alleged that he was subjected to mental harassment in custody and claimed personnel from Bengal's Special Operations Group (SOG) threatened him with a staged encounter and pressured him to confess.

Speaking to PTI at his residence in Ballia's Anand Nagar locality, Singh, who identified himself as the state general secretary of the Akhil Bharatiya Kshatriya Mahasabha, reiterated that he had no role in the killing and had been falsely implicated in the high-profile case.

"When the CBI conducted its investigation, I was found innocent. I have also got a clean chit from the court," he said, demanding an inquiry into the conduct of officials involved in his arrest and interrogation.

"Officials were saying they would shoot me. Whenever someone came near me, they would quietly show me a weapon. They were trying to intimidate me," he alleged.

Following his arrest on May 10 in Ayodhya, Singh's mother, Jamvanti Singh, had publicly maintained that her son was innocent and claimed to possess CCTV footage showing he was in Ballia on the day of the murder.

She had alleged that she and her son were detained by an SOG team while returning from Ayodhya after attending a wedding and visiting a dargah in Ambedkar Nagar district.