All the three have sustained self-inflicted injuries in the custody soon after they were arrested on criminal offence on Friday last, Superintendent of Police (city) Karthi S told a press conference here.
The accused were identified as Shamim alias Khande, having been charge sheeted in many cases in East Singhbhum, Modin alias Anna and Imran, both resident of adjoining Seraikela-Kharswan district.
Shamim attempted to cut vein on his forehead while the other two tried to slash vein on his wrist.
Police had also recovered a motorcycle and two two-weelers, all stolen articles from them, and one loaded 9mm pistol from Shamim.
Apart from the relevant section of IPC, Karthik said a case was also registered for attempting suicide against the three.
Police were also investigating how they could carry blade.