Speaking via Tongan radio, Prime Minister Hu'akavameiliku and Minister of Health Dr Saia Piukala held a media conference on Tuesday night to announce the news.
They confirmed that two cases of Covid-19 have been detected through routine testing at the wharf in Nuku'alofa.
Prime Minister Hu'akavameiliku ordered the lockdown.
Dr Saia Piukala said 50 people were tested as part of routine surveillance and the two positive cases were found.
