A jailed gangster threatened the superintendent of Patna Medical College and Hospital (PMCH) Lakhendra Prasad over phone, allegedly to implicate another don whose wife he had an affair with.

Police said Sonu Sah, lodged in Beur Central Jail, impersonated don Shankar Prasad and threatened Prasad on Monday for failing to pay Rs 50 lakh extortion money.

Upset over frequent threat calls and text messages, Prasad sought the intervention of Patna senior superintendent of police Manu Maharaaj, who formed a team to investigate the case. Preliminary investigations revealed that Sonu made the calls.

Sonu, who had an affair with Shankar's wife, obtained a SIM in the name of Shankar and subsequently made frequent extortion calls to the PMCH superintendent and other officials from behind the bars. "The idea was to put Shankar in jail so that he could meet the latter's wife without any problem after coming out of jail on bail," an investigating officer said.

Sonu made at least 10 calls on Prasad's mobile at his Rajiv Nagar residence on Monday. He sent three text messages to the doctor. " Paisa doge ya goli khaoge (Will you cough up money or take bullets)?" one of the messages read.

Patna senior superintendent of police (SSP) Manu Maharaaj said Sonu would be taken on remand for interrogation. Sources said Prasad had received extortion calls for the fourth time in two years. He had earlier served as civil surgeon of Patna. The last time, Prasad had got extortion calls was on July 18, 2016 for which Munna Kumar was arrested from Naubatpur in Patna rural.