WELLINGTON, New Zealand – A powerful magnitude 7.3 earthquake struck just off the coast of Vanuatu on Tuesday, causing widespread destruction in the South Pacific island nation as the injured were rushed to hospital and unconfirmed reports of injuries emerged.

A tsunami warning was lifted less than two hours after the quake. With communications still broken hours later and official information scarce, witness accounts of victims emerged on social media and through patchy phone calls.

The earthquake struck at a depth of 57 kilometers (35 miles) and was centered 30 kilometers (18 miles) west of Port Vila, the largest city in Vanuatu, a group of 80 islands that is home to about 330,000 people. The shock was followed by a magnitude 5.5 aftershock near the same location, and showers continued throughout the afternoon and evening local time.

It was not immediately clear how extensive the damage was, with phone lines and government websites down. In initial official information posted on social media hours after the quake, the geohazard agency said its monitoring systems were offline due to power outages.

Residents were asked to stay away from the coast for at least 24 hours – until the tsunami and earthquake monitoring systems were operational again. There were no confirmed reports of damage or casualties, but reports of widespread destruction filtered out on social media and in interviews.

Dan McGarry, a Port Vila-based journalist, told The Associated Press that he heard about a fatality in the quake from a police officer outside Vila Central Hospital. McGarry saw three people on stretchers “in obvious distress,” he said.

Doctors were working “as quickly as they could” in a triage center outside the emergency room, he added. But the nation is not prepared for a mass casualty event, McGarry said.

Videos shared by the Vanuatu Broadcasting and Television Corporation showed crowds outside the hospital. Telephone numbers for the police, hospital and other public bodies were not established.

Reports of people trapped in collapsed buildings also could not immediately be verified. A video posted on social media appeared to show crumpled buildings in Port Vila, including one that had collapsed onto cars. A spokesman for the Red Cross in Fiji said the head of the charity’s Vanuatu office reported widespread damage before communications were lost.

A building housing several diplomatic missions in Port Vila – including those of the United States, Britain, France and New Zealand – was significantly damaged, New Zealand’s Foreign Ministry said. A spokesman said officials were in the process of accounting for staff at the New Zealand High Commission.

The US Embassy’s Facebook page said its office was closed until further notice.

A video posted on social media showed the building had some structural damage, including dented windows and debris that had fallen from the walls onto the floor. Other photos and videos showed items and shelves falling to store floors and landslides that appeared to block some streets.

Katie Greenwood, the Fiji-based head of the Red Cross’s Asia-Pacific regional office, told the Australian Broadcasting Corp. that downtown Port Vila was full of large buildings and hotels.

“At the moment we have not heard from any victims, but I would be shocked if we don’t hear the bad news from Port Vila at some point,” she said.

McGarry said a “massive landslide” at the international shipping terminal would likely hinder the country’s recovery. The airport’s runway was also damaged, he said.

Because of Vanuatu’s location in a subduction zone – where the Indo-Australian tectonic plate moves beneath the Pacific plate – earthquakes of magnitude greater than 6 are not uncommon and the country’s buildings are designed to withstand earthquake damage.

“I think it could have been worse,” McGarry said. But this was “by far” the worst thing he had experienced in his 21 years in Vanuatu, he said.

Australian Foreign Minister Penny Wong told reporters that Australian High Commission staff were safe.

“We will provide any assistance needed,” she said. “I say to the people of Vanuatu: you are family and Australia is here to help.”

New Zealand Foreign Minister Winston Peters said 45 New Zealanders were registered in Vanuatu. Peters said his government was “deeply concerned” about the situation there.

Phone lines and government websites remained down and official channels were not updated, but reports of widespread destruction began appearing on social media within hours of the quake.