He had been suffering from throat cancer for the past five years.
An emergency meeting of the Central Working Committee of the Nepali Congress held on Sunday endorsed the condolence motion on the demise of leader Giri.
The meeting also decided to lower the party flag half-mast and not to conduct official functions for the next three days—August 21, 22 and 23—NC Chief Secretary Krishna Prasad Paudel said.
The meeting has also decided to close all the party offices on Monday.The party has also decided to hold condolence meetings in all districts, municipalities and VDCs on September 1.
Giri had returned to Nepal a few months ago after treatment for throat cancer at Hinduja Hospital in Mumbai, India.
He was admitted to the Mediciti Hospital a month ago after suffering from Pneumonia.
Dr Sandarbha Giri, who had been attending to Giri, said that he died at 9: 30 pm.