Disaster authorities in Tonga say power is off on the southern island of 'Eua but the main island of Tongatapu was relatively unscathed by Cyclone Keni.

Photo: RNZ / Richard Tindiller

The cyclone moved to the south-southwest of Tonga as a category three storm this morning.

However, National Emergency Management Director Leveni 'Aho said it was nearly 300 kilometres away from the main island so there were few reports of damage at this stage.

"There's a few powerlines down but I think most of the trees have been cleaned out two months ago so there is not that many trees down but I mean the wind wasn't as strong as compared to what happened in [Cyclone] Gita. But the island of 'Eua, some damages to the hospital there and also most of the power in 'Eua is off."

Police said up to half of the hospital's roof had been ripped off and one person had sustained minor injuries.

A few houses were also thought to have been damaged at Angaha.

Leveni 'Aho said he expected power to be restored to 'Eua and pockets of Tongatapu within the next few days.