Jaswinder Singh, a 69-year-old resident of Delhi, suffered a severe heart attack in the train at Chowki Shahdara Railway Station and died instantly, officials of a state-run rescue service said.
Singh was part of a group of Sikh pilgrims travelling from Nankana Sahab in Punjab, Pakistan to Lahore.
Hundreds of Indian Sikhs are visiting Pakistan to participate in events marking the death anniversary of Guru Arjan Dev at Gurdwara Panja Sahib in Hasanabdal.
A rescue team took the deceased's body to Mayo Hospital in Lahore.
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