Assa Singh is currently serving a 10-year jail sentence in a 1987 robbery case involving Rs 5.70 crore.
Reports said Assa Singh was attacked by fellow inmates in Hoshiarpur prison.
However, jail authorities said Singh suffered serious injuries when he fell down near the washroom.
Dal Khalsa head H S Dhami and his deputy Manjinder Singh met Assa Singh in the civil hospital here today.
Dhami said despite government orders that no one above 80 years would be imprisoned, Assa Singh had been languishing in jail.
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Urging the state government to consider his case on humanitarian grounds, Dhami said Assa Singh needed proper medical aid.
His condition was serious and he should be released immediately, Dhami said.
Flaying the jail authorities, he said they had failed to take up the case of aged and ailing person with the government in time.
To a question, Dhami said what happened to Assa Singh was a mystery.
Praying for his speedy recovery, he said "we have to wait for his condition to become stable for ascertaing what exactly happened to him.