Congress leader Shashi Tharoor said he was "saddened" by 1993 Mumbai serial blasts convict Yakub Memon's execution on Thursday."Saddened by news that our government has hanged a human being. State-sponsored killing diminishes us all by reducing us to murderers too," Tharoor tweeted."There is no evidence that death penalty serves as a deterrent, to the contrary in fact. All it does is exact retribution, unworthy of a Government," the Thiruvananthapuram MP added.He said: "... cold-blooded execution has never prevented a terror attack anywhere." Yakub Memon was hanged to death in Nagpur prison early Thursday. (CNS)