Australia and New Zealand are closely monitoring tropical Cyclone Gita, which has caused flooding and wind damage in Samoa and is still building.
A state of disaster has been declared in Samoa as authorities focus on rescue and evacuation in the wake of Cyclone Gita.
The cyclone tore through the country but is now moving away to the southeast.
Gita was expected to veer towards Niue overnight and pass close to the island's east coast.
From there, the cyclone was forecast to arc westward towards Tonga's main island, Tongatapu, on Monday.
Ulu Bismarck Crawley, head of Samoa's Ministry of Natural Resources and Environment, said the north coast and riverways prone to flooding were the worst hit.
There were no reports of injury or death and emergency services were focusing on people isolated by the storm.
Yesterday in Auckland, Australian foreign minister Julie Bishop said New Zealand and Australia had been briefed on the category-two cyclone in the southwest Pacific and were ready to assist.
Yesterday afternoon, UNICEF NZ tweeted: "We are monitoring the impact of Cyclone #Gita on Samoa, Niue, and Tonga, and ready to respond with emergency supplies if required."
Weather models suggested Gita would track further southward towards New Zealand next weekend, or early the following week.
WeatherWatch said weather models suggested Gita would track further southward towards New Zealand next weekend, or early the following week.
But it was too early to know if it would directly impact New Zealand's weather.
The cyclone would be stronger than Cyclone Fehi, which caused extensive damage on New Zealand's West Coast last weekend.
The US Joint Typhoon Warning Centre says winds will increase much more in the coming days, and forecast winds over 150km/h and gusts over 200km/h by mid next week.
The Samoa Red Cross said respondents had been sent to the south and Aleipata coasts of Upolu as telephone contact had been lost.
To the east, American Samoa power was knocked out in large areas and businesses and schools were ordered shut.
In news reports American Samoa's governor, Lolo Matalasi Moliga, said the cyclone had caused a lot of damage to homes and utilities.
Lolo made an emergency declaration and said it was likely the territory would ask for assistance from the United States.