Evacuations are underway in some areas of Vanuatu as Cyclone Judy crosses the country, bringing heavy rain and gale-force winds.
The system was upgraded from a category 3 to a category 4 storm after hitting the capital Port Vila on Wednesday morning.
Residents have reported minor damage so far.
Schools and businesses are closed and Air Vanuatu has cancelled all domestic and international flights, with flights expected to resume on Thursday.
On Wednesday morning, the Vanuatu Meteorology and Geo-Hazards Department warned of destructive hurricane-force winds of 150 kilometres per hour, gusting to 200kph, in the central and southern islands.
Heavy rainfall and thunderstorms are expected over the central, southern and parts of the northern islands, with flash flooding expected in low-lying areas.
The department also warned of rough seas, with heavy swells in Vanuatu waters.
On Tuesday night, Vanuatu Meteorology department manager Fred Jockley told the ABC the cyclone was slow-moving and almost "stationary".
"It will take probably until March 2 to move away from the country completely," he said.
The cyclone hit the island province of Pentecost, in the country's north-east, on Tuesday night.
The area is extremely remote, with limited phone or internet reception.
The northern part of Vanuatu, which the system hit early on Wednesday morning, is also experiencing connectivity issues.
Carol Rovo, the provincial emergency coordinator for Sanma Province, said people in some areas were evacuated to higher ground.
She said many people living in remote areas did not have access to cyclone warnings via radio or other communications, so her team visited those areas on Tuesday to make sure families were prepared.
"We are still in red alert. Some of our schools are still closed," Ms Rovo said, but she added the cyclone had begun to move away from the area, towards the southern provinces.
Dickinson Tevi, secretary-general of the Vanuatu Red Cross Society, said strong winds hit the organisation's office in Port Vila early this morning.
"It's currently quiet at the moment," he said.
"We don't know whether we are right in the eye of the cyclone.
"Are still more winds expected or has it gone past us? But there's a lot of people saying … probably we're in the eye of the storm."
Mr Tevi said he had ventured outside during the calm period, seeing some of the damage, including downed tree branches, radio wires and powerlines.
Power outages have been reported in several parts of the capital.
He said Red Cross emergency response teams in all provinces had been put on high alert and were preparing an emergency plan of action.
"As soon as the cyclone passes, we will put this emergency plan in place and we should be ready with a response," he said, adding that only minor damage was expected.
Local journalist Dan McGarry said the storm was intensifying as it hit open water and was moving south towards two major population centres, including Tanna.
"They know this storm is coming, they know it's going to be stronger there … so they're expecting some very high winds and very rough seas."
