An earthquake of magnitude 6.1 has struck the Vanuatu islands, the second quake to hit the tiny Pacific nation in 24 hours, the GFZ German Research Centre for Geosciences said.
The quake struck early on Wednesday at a depth of 10km, the GFZ said.
While the full extent of the devastation in Vanuatu remains unclear, Australia will be among the countries deploying assistance to the Pacific island nation.
At least 14 people have died and hundreds are injured, according to the Red Cross.
National broadcaster VBTC showed footage of vehicles crushed under the debris of collapsed buildings and boulders strewn across a highway. Drone footage showed landslips near a shipping terminal.
On Tuesday evening, Vanuatu's caretaker, Prime Minister Charlot Salwai, declared a state of emergency and said a curfew would be imposed for seven days in the worst affected areas. International assistance has been requested.
It was a "sad and devastating time" in Port Vila, he said, expressing sympathy to families who had lost loved ones.
'We are family'
Australian Foreign Minister Penny Wong called the disaster a "dreadful tragedy", and acting Pacific Minister Matt Keogh said Australia would be rushing to its neighbour's aid.
"Australia stands with the people of Vanuatu ... we are family, and we will always be there in times of need," the pair said in a statement.
"Early reports indicate that significant damage has occurred. The Australian government is preparing to deploy immediate assistance (from Wednesday), including urban search and rescue and emergency medical teams.
"We are closely monitoring the situation and stand ready to provide further assistance to the people of Vanuatu as the extent of damage becomes clear."
Rescue efforts to find people trapped in collapsed buildings continued on Tuesday evening, a police official told local media.
"It was the most violent earthquake I've experienced in my 21 years living in Vanuatu and in the Pacific Islands. I've seen a lot of large earthquakes, never one like this," Dan McGarry, a journalist based in Vanuatu, told news agency Reuters.
The La Casa D'Andrea E Luciano building, which houses the United States, United Kingdom, French and New Zealand embassies and high commissions, has been seriously damaged, with footage posted to social media showing a section of the building collapsed onto the first floor.
France's Pacific envoy Véronique Roger-Lacan shared on social media that diplomatic personnel were unharmed.
Other photos and videos published by VBTC show minor damage, including shattered windows and walls and rearranged interiors.
McGarry posted drone footage of major landslides near Vanuatu's international shipping terminal.
McGarry told AAP there was no doubt there had been casualties from the tremor.
"There are buildings down here, so I'm expecting the casualty figure to rise," he said.
"I know of one fatality, according to police stationed at Port Vila Central Hospital, and I saw with my own eyes three others on gurneys, several others walking around, walking wounded.
"I think it will probably be in the dozens, altogether dead and wounded."
The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) estimated 116,000 people had been affected by the earthquake.
The structure of the hospital in Port Vila was affected, with the operating theatre not functioning and triage tents set up outside to manage the influx of patients, OCHA said in a statement.
Authorities were unable to communicate with the National Disaster Management Office until Tuesday evening, when Starlink satellite services were provided, it said.
The earthquake occurred at a relatively shallow depth of 57km, according to earthquake monitors, the United States Geological Survey.
Smaller aftershocks, including one of 5.5 magnitude, followed.
The island nation lies on the "Ring of Fire", a 40,000km seismically active arc around the rim of the Pacific tectonic plate.
Kasper van Wijk, associate professor of Physics at the University of Auckland, said: "Vanuatu is situated, like New Zealand, on top of a subduction zone."
"This particular earthquake was shallow and close to Port Vila, so I expect there to be significant damage from the earthquake."
Australia's foreign affairs department advises Australians requiring consular assistance should contact their 24-hour
on +61 2 6261 3305.
