According to hospital authorities, Swu, 85, died at 12.40 p.m at the Fortis hospital.
He was admitted to the Vasant Kunj-based Fortis on July 5, 2015, where he underwent a series of surgeries including for urinary tract infection.
Speaking to IANS, his son Pasheto said: “Yes, Sadly it is true that dad (Isak Chisi Swu) passed away today. His body will be flown back to his ancestral village in Nagaland soon.”
Isak Chisi Swu was co-founder of NSCN-IM along with T. Muivah.
Due to his illness, Swu could not attend the inking of the historic Naga Peace Accord on August 3, 2015 with the Government of India at the official residence of Prime Minister Narendra Modi.
Swu, formerly member of Naga National Council (NNC) and later the National Socialist Council of Nagalim (NSCN), was born in 1929 in Chishilimi Naga village in the Zunheboto district of Nagaland.
His death comes at a time when the NSCN (IM) and the Indian government are still negotiating for the final conclusion of the Naga Peace Accord.