The four persons had gone to the river bank at Neematighat to collect hay and vegetables when they were attacked by the leopard, the officer said.
The four have been admitted to the Jorhat Medical College Hospital and their condition is stated to be critical. Two of them were later referred to Assam Medical College Hospital, Dibrugarh, the officer said.
The injured have been identified as Bokul Das, Dhoniram Das, Moina Das and Mohan Das.