The man has been admitted to a hospital in Guwahati, Assam for further treatment.
After the person was found positive the entire Marwaripatti and Ghorapatty areas in Dimapur were sealed. As a precautionary measure, Zion Hospital, Dimapur where the patient was earlier admitted has also been sealed. Doctors, nurses, support staff and their family members who came into direct and indirect contact with the patient to be quarantined.
Family members of the patient have already been shifted to the government quarantine centre.
"A man from Nagaland has tested positive for COVID-19. He travelled from Kolkata to Dimapur on March 24, after which he was home quarantined," the state government said in a statement.
The statement added that the wholesale market at GS Road Dimapur and retail shops at Marwaripatti and Ghorapatty will be closed until further orders.
The parents and family members of the patient who are presently in Guwahati are undergoing necessary tests.
The government has also started contact tracing for all passengers who were on the same flight taken by the patient on March 24.
Assam Minister Himanta Biswa Sarma earlier tweeted, "A private hospital in Dimapur, Nagaland referred a patient to GMCH after he was found with symptoms of #COVID19. He has tested positive and is undergoing treatment".
( With inputs from ANI )