Cyclone Gita is gathering strength as it heads towards Tonga and is expected to be a category five storm by the time it reaches the Pacific nation.
The cyclone has already carved a swathe through American Samoa and Samoa, with large-scale clean-up efforts underway in both countries.
Tonga's government has now declared a state of emergency.
People in flood-prone or low-lying parts of Tonga are being urged to leave their homes before the cyclone makes landfall, forecast for about midnight.
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