Wellington - Tonga was battening down on Friday as a powerful tropical cyclone bears down on the Pacific island nation, officials said.
Tropical Cyclone Ian, a category four system packing winds of up to 230km/h, was expected to make landfall early on Saturday, the UN office for the co-ordination of humanitarian affairs (OCHA) said.
"The cyclone may cause destructive winds, heavy rain, high swells and flash flooding in low-lying coastal areas", it said, adding that many people were boarding up windows and cutting back trees to minimise potential damage.
Red Cross emergency teams were on standby.
Tonga's national emergency operations committee advised people to stock up on enough food and water to last for three days.
Tonga's 105 000 residents are used to dealing with cyclones, which are common in the Pacific during the November-April hurricane season.
Cyclone Ian has been lying offshore between Fiji and Tonga in recent days as a category three storm but has intensified as it approaches land.