Anjan Dutta, president of the Assam state unit of the Congress, died on Thursday of a cardiac arrest in New Delhi, doctors said.
Dutta, a former transport minister of Assam and three-time legislator from the Aamguri constituency, was undergoing treatment since May 25 at the All India Institute of Medical Sciences (AIIMS) in New Delhi under pulmonary medicine expert Randeep Guleria.
"He died today morning at 7.15 a.m. and his body has been sent to the mortuary now," a senior doctor of the AIIMS said.
Assam Pradesh Congress Committee (APCC) members in Guwahati said Dutta went to South Africa after the Assam assembly elections in April and fell sick on his return.
He was initially admitted to the Apollo Hospital in New Delhi and subsequently shifted to the AIIMS. Congress vice president Rahul Gandhi had visited Dutta at the medical institute.
Dutta became the Assam state Congress president in December 2014.
"It is a shocking news for all of us. We were aware about the ill health of Dutta but this was not expected," said Assam Congress spokesperson Apurba Bhattacharyya.
He said Dutta's body will be brought on Thursday to Rajiv Bhavan in Guwahati, where party leaders will pay tribute to the departed leader. The body will then be taken to his home in Sivsagar district for cremation on Friday.