A national emergency officer in Tonga says disaster management plans have been activated as Cyclone Ian closes in.
On Friday evening, the cyclone was about 185 km northwest of the Vava'u islands and with average wind speeds of 157 km/h close to the centre and momentary gusts of 222 km/h.
Ian has been ugraded from a category 3 to a category 4 cyclone.
The director of Tonga's National Emergency Management Office, Leveni 'Aho, said people living in the outer islands have been on stand-by since the cyclone first surfaced on Monday.
The cyclone is expected to pass close to the Vava'u and Ha'apai groups. Communities are taking action, including evacuating patients from a waterfront hospital in Ha'apai.
Mr 'Aho says resorts throughout the island groups are all aware of the situation.