BJP President Amit Shah has expressed grave concern over the alleged attacks on party workers in the constituency of Kerala Chief Minster Pinarayi Vijayan.<br/><br/>In a series of tweets, Mr Shah said the killing of a BJP worker in Kannur district of the State is disturbing. <br/><br/>He said, political vendetta is behind the killing. Mr Shah also offered his condolence to the family of the deceased party worker.