Goa police has started investigations into an anonymous letter signed by ISIS that says the terror outfit will kill PM Narendra Modi and defence minister Manohar Parrikar for banning beef in India."Since you are not allowing to eat beef, you will be taken care of," the postcard said while referring to Modi and Parrikar, reports timesofindia.The letter was received at the home and general administrative departments.Speaking to TOI, IGP V Renganathan said that they have initiated an inquiry into the matter. He also said that in the letter it was stated that since you have banned cow killing, we will see you (Modi and Parrikar).Renganathan confirmed the probe by the anti-terror squad and added that the postcard was posted locally.Police also said that they have decided to step up Parrikar`s security in the state.