China offered a cash donation to Tonga on Monday after a volcanic eruption and tsunami hit the South Pacific country on Saturday, blocking communications and leaving some 105,000 residents on the islands virtually uncontactable.

"The Red Cross Society of China has decided to provide $100,000 of emergency humanitarian assistance in cash to Tonga," said Foreign Ministry spokesman Zhao Lijian on Monday.

"China is very concerned about the disaster in Tonga caused by the volcano eruption, and extends deep sympathy and sincere condolences to the Tongan government and people for the severe loss brought by the disaster."

China will provide further assistance within its ability to Tonga according to the situation and needs of Tonga, he added.

On Monday, Australia and New Zealand dispatched surveillance planes to assess the damage in Tonga with initial reports saying that "there were no mass casualties but significant damage to coastal properties and resorts".

Zed Seselja, Australia's minister for the Pacific, said there were no mass casualties, but Australian police have visited beaches and found significant damage with "houses thrown around".

Seselja also said surveillance flights assessed the situation on outer islands where communications were completely cut off. The flights, along with detailed pictures and videos, were due back in Australia and New Zealand on Monday evening.

One British woman named Angela Glover was reported missing after being swept away by a wave. Her husband, who went with her to get their dogs, managed to hold onto a tree. Their dogs were also swept away.

Resort 'wiped out'

Ha'atafu Beach Resort, on the Hihifo Peninsula, 20 kilometers west of Tonga's capital Nuku'alofa, was "completely wiped out", wrote its owners on Facebook.

Meanwhile, two people drowned off a beach in northern Peru due to high waves caused by the tsunami.

Saturday's eruption had caused tsunamis to flood coastlines from Japan to the United States, with some of them reaching heights of 3 meters.

On Monday, Curtis Tu'ihalangingie, Tonga's deputy head of mission in Australia, asked for patience as the Tongan government decides its priorities for aid.

Tonga is concerned about the risk of aid deliveries spreading COVID-19 to the island which is free of the virus.

"We don't want to bring in another wave－a tsunami of COVID-19," Tu'ihalangingie said by telephone. "When people see such a huge explosion, they want to help."

Agencies contributed to this story.