An earthquake of magnitude 7.3 has struck near Port Vila, Vanuatu, on Tuesday, the US Geological Survey said.

The quake struck at a depth of 43 kilometres, 30km west of Port Vila, the USGS said. It was reviewed down from 7.4. The jolt was followed by a magnitude 5.5 aftershock at the same location.

The extent of any damage was not immediately clear. Footage posted on social media showed buckled windows and collapsed concrete pillars on a building hosting the US and some other foreign embassies in the capital, not including Australia.

Treasurer Jim Chalmers said Australian officials were still gathering information about the situation on the ground.

“We are aware of the news of a very significant earthquake near Port Vila,” he said. “We know there is now a very serious threat of tsunami.

“That’s a beautiful country and it is under threat right now. We are thinking of the wonderful people of Vanuatu who are worried now, battening down the hatches.”

Vanuatu government websites were offline in the aftermath of the quake and phone numbers for the police and other public agencies did not connect, Associated Press said.

The USGS warned of tsunami waves for some coasts on Vanuatu, a group of 80 islands that is home to about 330,000 people. Waves could reach 30cm to 1 metre above the tide level, the agency said.

Some islands in the low-lying atoll nation are 1m above sea level.