"The incident took place when Parbatsinh Amarsinh Koli (40) was taken out of the cell for bathing along with other prisoners," Radhanpur sub-jailor K L Desai told PTI.
"Koli then headed towards toilet and hanged himself with the clothes he was wearing in the toilet," Desai said.
A native of Karai village in Nagarparkar taluka of the same district in Pakistan's Sindh province, Koli was held by the Border Security Force from 'pillar No 982' in Indian territory before being handed over to the state police in 2012.
He had escaped from the lock-up but was later re-arrested near Gotarka village in Radhanpur taluka of Patan district, Desai said.
"From January 20 this year, he has been lodged in Radhanpur sub-jail," he added.
When contacted, Patan Superintendent of Police (SP) Saurabh Tolambia confirmed that Koli had committed suicide but said that a panel of doctors has been asked to carry out the post-mortem to ascertain the exact cause of the death.