Congress' Jalandhar MP Santokh Singh Chaudhary died on Saturday after suffering a cardiac arrest during the Bharat Jodo Yatra, following which the march was halted.
He was 76.
The two-time MP was taking part in the Rahul Gandhi-led march in Phillaur in Jalandhar where he fainted, said senior party leader Partap Singh Bajwa, who was also marching in the yatra.
He said Chaudhary was rushed to a hospital in Phagwara in an ambulance.
The yatra was halted following Chaudhary's death and it is learnt that Gandhi has gone to the hospital.
Earlier in the morning, the yatra resumed from Ladhowal in Ludhiana as part of its Punjab leg.
Punjab Chief Minister Bhagwant Mann expressed grief over the death of the Congress MP.
"I am deeply saddened at the untimely death of Congress Member of Parliament from Jalandhar, Santokh Singh Chaudhary," he said in a tweet in Punjabi.
Former Congress leader Amarinder Singh also condoled Chaudhary's death.
"Extremely saddened to hear about the sudden demise of MP Santokh Singh Chaudhary ji due to a heart attack today. My heartfelt condolences are with his entire family in their time of grief. May Waheguru Ji grant eternal peace to the departed soul," said Singh in his tweet.
Congress president Mallikarjun Kharge said Chaudhary's passing away is a great blow to the organisation.
"Deeply shocked and saddened to learn about the untimely passing away of our MP, Shri Santokh Singh Chaudhary. His loss is a great blow to the party and organisation. In this hour of grief, my heart goes out to his family, friends and followers. May his soul rest in peace," Kharge said on Twitter.
Several Congress leaders have gone to the hospital.
The Punjab leg of the march begun on Wednesday from Sirhind in Fatehgarh Sahib.