Dhanbad, March 14: Dhanbad police arrested a hitman last night and claimed to have blown the lid off a plot to kill a local contractor by monitoring cell phone conversations of a notorious gangster and his henchmen who are all in jail.

Police said sharpshooter Rinku Khan, alias Amir, was working for Fahim Khan, a gangster who is in Hotwar jail in Ranchi for murder, and three of his henchmen, who are in a Dhanbad jail.

Dhanbad deputy superintendent of police (DSP) Amit Kumar, the man behind Rinku's arrest last night from Dhanbad's Bank More, said that the order to first threaten and then kill railway contractor A.K. Jha was given by Fahim's son Iqbal, who is in Dhanbad jail along with Gopi Khan and Prince Khan.

DSP Kumar said a railway contract worth Rs 25 lakh was at the centre of the dispute. Fahim, who the police say runs his gang from the Hotwar jail using SIM cards obtained through forged documents, did not want Jha to pursue the railway contract.

Fahim had asked Rinku to first negotiate a pullout with Jha, but kill him if he refused.

'Jha's refusal to let the contract go was communicated to the Khans in Dhanbad jail after which Iqbal told Rinku to kill him,' said the DSP, whose team is said to have monitored their cell phone conversations.

'As Rinku was moving towards the Bank More area, apparently looking for Jha, our team nabbed him late last night,' he said, adding that Rinku was then shifted to the local station for interrogation.

Police have lodged cases against Rinku, Iqbal, Gopi and under IPC sections 387 (extortion, threatening a person with death) 467, 468 and 471 (forgery of documents).

DSP Kumar told The Telegraph that the criminal trio in Dhanbad jail were using the mobile number, 7858834037, to stay in touch with Rinku. This number was also used when the final order to Rinku to kill Jha was given.

Police sources said the trio used another number, 7870662155, to often make extortion calls and ransom demands to local businessmen and traders.