By Ben McKay in Darwin

A major casualty event is feared in Port Vila after a brutal earthquake rumbled Vanuatu’s capital, damaging buildings including a diplomatic hub.

A magnitude 7.3 earthquake struck just off the coast of Vanuatu’s major island of Efate on Tuesday afternoon.

Locals reported on social media feeling violent shaking for around 30 seconds.

Broadcaster VBTC has reported a number of destroyed buildings, some of which have fallen on and crumpled cars.

The La Casa D’Andrea E Luciano building, which houses the US, UK, French and New Zealand embassies and High Commissions, has been seriously damaged, with footage posted to social media showing a section of building collapsed onto the first floor.

France’s Pacific envoy Veronique Roger-Lacan posted 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.

Dan McGarry, a Vanuatu-based journalist, posted drone footage of major landslides near Vanuatu’s international shipping terminal.

He 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.”

Attempts to confirm fatalities or injuries with Vanuatu authorities have been unsuccessful, owing to communications issues.

AP reported government websites were offline in the immediate aftermath of the tremor, as were local media outlets.

“There is limited connectivity through one of our telecommunications carriers, the other one is entirely offline and power is out through the entire capital,” Mr McGarry said.

Foreign Minister Penny Wong said the Australian government was closely monitoring the situation in Vanuatu following the quake.

New Zealand Foreign Minister Winston Peters confirmed “significant damage” to the diplomatic building, along with his “deep concerns” following the significant tremor.

Treasurer Jim Chalmers, speaking to media shortly after the disaster, said the earthquake was “very serious” and “very troubling”.

“I’m confident I speak on behalf of all Australians when I say that we are thinking of the wonderful people of Vanuatu,” he said.

A tsunami threat to Australia and New Zealand was cleared by authorities in both countries.

The earthquake occurred at a relatively shallow depth of 57km, according to American earthquake monitors the United States Geological Survey (USGS).

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.

“Vanuatu is situated, like New Zealand, on top of a subduction zone,” University of Auckland physics associate professor Kasper van Wijk said.

“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 that Australians requiring consular assistance should contact the their 24-hour Consular Emergency Centre on +61 6261 3305.