Patna: The spectre of bloody clashes is looming over north Bihar as supporters of gangster Santosh Jha, who was murdered in the Sitamarhi court premises on Tuesday, are seething for revenge.

Highly placed sources said that Vikas Jha alias Kalia, who was accompanying Santosh at the time of his production in the Sitamarhi court on Tuesday, has vowed to avenge the killing of his mentor Santosh.

Gangster Mukesh Pathak, once considered a close associate of Santosh, is believed to be the mastermind behind the murder of Santosh. Police sources said Pathak, who is lodged in the Sitamarhi district jail, roped in juveniles facing criminal charges to eliminate Santosh.

Both Mukesh and Santosh were awarded life terms in the Darbhanga engineers' double murder case.

Collection of extortion money from contractors of nine districts in north Bihar is stated to be the reason behind the murder of Santosh.

"Mukesh decided to get Santosh eliminated as he wanted to establish his supremacy over the 40-member gang mainly involved in extortion and contract killing," a senior police officer said on Friday.

The officer said Mukesh provided illegal weapons to juveniles to kill Santosh court. On Friday, a man was arrested from Chakia in East Champaran district; the police said the arrested man is the brother of a juvenile involved in Santosh's murder.

"It was this man who had helped his younger brother, a juvenile, get released from the Motihari remand home to kill Santosh in judicial custody," Sitamarhi superintendent of police Vikas Burman told The Telegraph.

Vikas Mahto, one of the killers of Santosh who was nabbed on the court premises after the murder, had told the cops that Mukesh had assigned the job to a sharp shooter named Prince.

Prince and two others are absconding.

Sources said Kalia was seething with anger after the killing of his mentor Santosh. "This has given credence to people's apprehension of a fresh gang war in north Bihar," an investigating officer said.

The officer, who is closely monitoring the Santosh murder probe, said two of the shooters had taken leave from the remand home in Motihari on the pretext of meeting ailing relatives. Police sources said Mukesh, who married a prisoner while being lodged in the Sheohar jail, ensured that the juveniles were imparted proper training before they were assigned the task.

Sources said Santosh and Mukesh fell out soon after their conviction in the Darbhanga double murder case.