Wellington: Nearly 2,000 people took refuge in emergency shelters and one man was missing after being swept away in floodwaters as Tropical Cyclone Sarai pounded Fiji on Saturday causing widespread damage.

National Disaster Management Office Director Vasiti Soko urged locals and the thousands of tourists in Fiji not to be reckless as Sarai lashed the Pacific island nation with heavy rain and destructive winds.

With wind gusts strengthening to 150 kilometres (93 miles) per hour during the day, Sarai destroyed houses and crops, brought down trees, cut power and caused considerable flooding in low-lying areas.

Thousands of holidaymakers were stranded with flights to and from Fiji either cancelled or rescheduled.

New Zealander Melonie Sheppard, who was holidaying on Mana Island to the west of mainland Fiji, described the situation as "scary" and said their resort was in lockdown.

"We're being hammered by intense winds and horizontal rains. The resort is providing packed meals and water direct to rooms when they can," she told the New Zealand Herald.

"Wind is howling and tree debris flying about, doors and windows shaking, huge waves rolling into shore. Water now leaking into some rooms - it's a bit scary at times."

The Fiji government issued a statement warning of "destructive force winds with... coastal sea flooding to be expected."

The National Disaster Management Office said as of mid-morning on Saturday, 1,970 people had sought emergency shelter and there had been no reports of any injuries.

However, there were fears for the safety of a man swept away as he tried to cross a flooded river while another man, reported missing at sea, was rescued in his fibreglass dinghy by police.

Acting police commissioner Rusiate Tudravu said it was disappointing that some people had disregarded the weather warnings.

"People themselves are irresponsible... we issued a warning prior to the cyclone through the relevant authorities, yet people saw it fit for themselves during the cyclone to take such irresponsible actions," he said.

On its present track, the cyclone is forecast to pass adjacent to Fiji's main island Viti Levu, then across Fiji's southern islands before heading towards Tonga, which has activated its tropical cyclone warning centre with the storm expected to arrive late Sunday.