Senior CPI-M leader P. Jayarajan has been summoned by the CBI to appear before investigators on June 2 in connection with an RSS activist's murder last year, CBI sources said. Jayarajan is the Communist Party of India-Marxist's Kannur district secretary.  RSS activist K.T. Manoj, one of the people accused of making an unsuccessful bid on the life of Jayarajan in 1999, was attacked by a seven-member gang on September 1, 2014, in Kathirur near Kannur.  His asailants first threw a bomb on the RSS activist's vehicle and later hacked him to death.  Kerala Police probed the case that was later handed over to the Central Bureau of Investigation (CBI) to look into the conspiracy angle. So far, 19 people have been arraigned as accused.  The murder shook Kannur district, for long a hotbed for political murders on account of fierce rivalry between the CPI-M and the BJP-RSS combine. With a BJP government led by Prime Minister Narendra Modi at the Centre, the state BJP leadership swung into action. Union Home Minister Rajnath Singh went to the murdered activist's home, and soon thereafter a green signal for the CBI probe was given on the Kerala government's request.  One of the powerful CPI-M leaders, Jayarajan is being summoned by the CBI at a time when he is already out on bail in the Shukoor murder case.  Jayarajan secured bail in the case after remaining in Kannur jail for close to four weeks in August 2012.  With IANS