A state of emergency has been declared in Tonga, the island nation to the north of New Zealand, as Cyclone Ula unleashes flash floods, torrential rain and thunderstorms and winds reaching up to 200kmph (124mph). Hundreds of islanders have now been forced to flee their homes in one of the worst disasters ever to hit the Polynesian kingdom ruled by Tupou IV.

As of 2 January no casualties have been reported, however, damage to property is widespread as houses have their roofs ripped off and crops have been unearthed.

"We are very happy that there are no casualties, police checked with hospitals and town officers to confirm that," the chairman of the National Emergency Management Office, Siaosi Sovaleni, told a press conference. He added: "We had 11 evacuation centres and over 390 people were relocated to these evacuation centres."

Coach of Fiji's national rugby union team the Fiji 7s Ben Ryan took to Twitter and said: "Cyclone Ula battering a lot of the Pacific right now – stay safe everyone and prayers with you."

Prime Minister Akilisi Pohiva has declared a state of emergency for the Vava'u and Ha'apai islands and more islands are expected to follow.

A statement from aid organisation UNICEF, said: "At 6am this morning Cyclone Ula was just 50 north of the Vava'u group in the central part of the Kingdom of Tonga. The country is on high alert and the Vava'u and Ha'apai islands have declared a state of emergency."

Ula formed early on Thursday in the South Pacific Ocean between Tuvalu and Samoa and was first classed as a category one storm as it tracked west-south-westerly, it has now been upgraded to a category three storm due to its intensity.

The director of the Tonga meteorological office, Ofa Fa'anunu, has said that the island could face the worst form of storm: a category five cyclone. The storm system is expected to weaken tomorrow (3 January) as it heads towards Fiji.