The Government issued a public notice, announcing restrictions which include a midnight to 5am curfew, two metre social distancing rules, and restrictions on funeral gatherings.
The lockdown is in effect until 9 May.
There are currently no Covid transmissions on Niuafo'ou, Niuatoputapu and 'Eua, according to the latest Covid update from the Ministry of Health.
As of Sunday, there were a total of 1,759 active cases and 113 new cases, a significant decline in Covid numbers from last week.
The official death toll remains at nine.