New Delhi, Aug 7: Prime Minister Narendra Modi on Tuesday expressed his anguish over the death of DMK President M. Karunanidhi.In a series of tweets, Modi said: "Deeply saddened by the passing away of Kalaignar Karunanidhi. He was one of the senior most leaders of India."We have lost a deep-rooted mass leader, prolific thinker, accomplished writer and a stalwart whose life was devoted to the welfare of the poor and the marginalized."Kalaignar Karunanidhi stood for regional aspirations as well as national progress. He was steadfastly committed to the welfare of Tamils and ensured that Tamil Nadu's voice was effectively heard," Modi said.Modi said he had the opportunity of interacting with Karunanidhi on several occasions. "His understanding of policy and emphasis on social welfare stood out. Firmly committed to democratic ideals, his strong opposition to the Emergency will always be remembered."