A Congress Seva Dal functionary died after collapsing during the party's Bharat Jodo Yatra in Maharashtra's Nanded district on Tuesday, a senior official said.
Senior Congress leader Rahul Gandhi, who is leading the foot march, expressed grief over the death of Seva Dal general secretary Krishna Kumar Pandey.
He said Pandey held the national flag till the very last moment.
"His dedication towards the country will keep inspiring up," Gandhi said, while extending condolences to Pandey's family.
While walking with senior Congress leader Jairam Ramesh and others, Pandey felt shortness of breath and uneasiness, a senior district official said.
Pandey was taken in an ambulance to Shankar Nagar primary health facility where doctors declared him dead, the official said, adding the deceased was a resident of Nagpur.
The body was later taken to Naygaon rural hospital for postmortem, he added.
Senior Congress leader Jairam Ramesh said Pandey was holding the tricolour and walking with him and party veteran Digvijaya Singh.
"After a few minutes, as is the practice, he handed the flag to a colleague and moved back. Thereafter he collapsed and was taken in an ambulance to a hospital where most sadly he was declared dead," Ramesh tweeted.
"He was a staunch Congressman and used to take on the RSS in Nagpur. It is a most humbling moment for all the Yatris," Ramesh added.
"The Yatris, Maharashtra Pradesh Congress Committee and @RahulGandhi paid last respects to Krishna Kumar Pandey this afternoon at the Yatra halt site in Atkali village in Nanded district," Ramesh said in another tweet.
Former Maharashtra chief minister Ashok Chavan also condoled Pandey's death, saying the party has lost a "staunch and loyal warrior".
The Congress's Bharat Jodo Yatra arrived in Maharashtra on Monday night and entered its 62nd day on Tuesday.
Gandhi visited Gurdwara Yaadgari Baba Zoravar Singh ji Fateh Singh ji on the occasion of Guru Nanak Jayanti a few hours after the yatra entered Maharashtra on Monday night from neighbouring Telangana.
At the gurdwara, Gandhi prayed for harmony and equality, the party tweeted.
During the yatra on Tuesday, Gandhi was flanked by senior Maharashtra Congress leaders including former chief ministers Sushilkumar Shinde and Ashok Chavan, state party chief Nana Patole, and other leaders like Balasaheb Thorat, Manikrao Thakre and Naseem Khan.