Swami Atmasthananda, the head of the Ramakrishna Math and Mission, passed away on Sunday. The 98-year-old monk had undergone treatment for age-related ailments since February 2015. The last rites will be completed at Belur Math this evening. Despite the best medical attention, his condition deteriorated over the last few days and he passed away at Ramakrishna Mission Seva Pratishthan Hospital, Ramakrishna Math and Ramakrishna Mission, Belur Math said in a statement. Prime Minister Narendra Modi condoled Atmasthananda's demise, calling it a personal loss. PM Modi considered him as his guru as he got spiritual guidance from Swami Atmasthananda in Rajkot in Gujarat. West Bengal Governor Keshari Nath Tripathi and Chief Minister Mamata Banerjee also condoled the demise of the monk. Swami Atmasthananda Maharaj was a seer. He was also attached to social causes. Under his stewardship, major relief operations were conducted in various parts of India, Nepal and Bangladesh during natural calamities. Atmasthananda was born on May 10, 1919, at Sabajpur, near Dhaka, now in Bangladesh. He had received mantra diksha from Swami Vijnanananda Maharaj (a monastic disciple of Ramakrishna) in 1938 and joined the Ramakrishna Order at Belur Math in January, 1941 at the age of 22. In 1945, Swami Virajananda Maharaj, the sixth president of the Order, gave him brahmacharya vows, and in 1949, sanyasa vows and the name Swami Atmasthananda. After serving the Order at Belur Math and the branches at Deoghar (Vidyapith) and Mayavati (Advaita Ashrama), Atmasthananda got the opportunity to serve Swami Virajananda Maharaj, the then president of the Order, for a long time. Watch this video He had spent several years in the company of Virajananda Maharaj at the Shyamla Tal in the Himalayas. In 1952, he was posted to Ranchi TB Sanatorium branch as an assistant secretary. In 1958, he was sent to Rangoon (Yangon) in Burma (now Myanmar) Sevashrama as its secretary. When military rulers took over the Rangoon Sevashrama, he returned to India in 1965 and was posted at the Rajkot branch as its head in 1966. He was elected a trustee of the Ramakrishna Math and a member of the governing body of the Ramakrishna Mission in 1973, according to PTI report. In 1975, he was appointed an assistant general secretary of the twin organisations. Under his leadership as relief secretary, the math and mission conducted massive relief and rehabilitation operations in various parts of India, Nepal and Bangladesh during natural calamities. He became the general secretary of the math and mission in 1992 and remained at that post for five years till 1997 when he became a vice-president of the Order. He was elected president of the Ramakrishna Math and Ramakrishna Mission in December 2007.