The judge who sentenced four Maoists to life term for the 2002 killing of Rohtas divisional forest officer Sanjay Kumar Singh has been threatened with murder.

A group of suspected Maoists have threatened to kill additional district and sessions judge Prabhunath Singh over his sentencing on Wednesday - employees of Sasaram civil court in Rohtas district found a pamphlet pasted on the wall of the court building on Friday. The pamphlet has warned the judge of "punishment" in a kangaroo court.

Singh on Wednesday sentenced self-proclaimed area commander Nirala Yadav and three more Maoists to life imprisonment for the forest official's murder in February 2002, and the fifth accused Sudama Oraon to 10 years' rigorous imprisonment.

A senior police officer said police seized the pamphlet and lodged an FIR with Sasaram Model police station against unidentified persons. "The security around the court has already been stepped up in the wake of the harsh punishment awarded to the Maoists in the DFO murder case," the police officer said.

Sasaram sub-divisional police officer Alok Kumar said a metal detector machine had also been installed at the gate of the civil court on the day of the sentencing. In addition, special auxiliary police and the Bihar Military Police personnel have been deployed.

A number of women cops and policemen in plainclothes have been deputed to keep an eye on criminals. "We are cautious and will leave no stone unturned to ensure security to the judicial officials," Alok told The Telegraph over phone.

The police headquarters has asked all superintendents of police to take precautionary measures to avert any untoward incidents, as the threat to additional district and sessions judge Singh is not an isolated incident.

District and sessions judge (I) of Munger Jyoti Swaroop Srivastava had received a similar threat from Maoists in May this year after Srivastava sentenced five Maoists to death for killing two CRPF personnel in blasts during the 2014 Lok Sabha election in Munger.

The Maoists had threatened the judge to try him in a "jan adalat (kangaroo court)" and award him "capital punishment". A letter circulated by the Bihar-Jharkhand Seemant Zonal Committee of the Maoists had also called for a mass agitation against the court order.

The incumbent chairman of the Rohtas district Bar council, Ram Murti Singh, on Friday termed the security on the Sasaram civil court premises inadequate.

"The advocates and the judicial officials are working under constant threat," he said, lamenting that security had not been strengthened even after two incidents of bomb explosions - one inside the court premises and another outside.

Lives were lost but the advocates' demand for more security fell on deaf ears of the police official, Ram alleged.

He said the Bar council would seek intervention of top police officers if their demand for adequate security on the court premises was not conceded at the earliest.

"It has become impossible for lawyers to work under such conditions," he said.