Cambodia has announced that fully vaccinated foreign travellers can visit the kingdom without quarantine from Monday, giving a boost to the Covid-hobbled tourism industry.

Travel restrictions imposed to tackle the pandemic put the brakes on Cambodia's burgeoning tourism industry -- revenue plummeted to $1 billion last year, down from nearly $5 billion in 2019, when the country attracted 6.6 million visitors.

Prime Minister Hun Sen made an unexpected announcement on Sunday night that all fully vaccinated international travellers, tourists and businesspeople could visit the whole of Cambodia freely without quarantine from Monday.

The decision overrode the previous reopening plan, under which popular beach spots Sihanoukville and the island of Koh Rong, as well as Dara Sakor -- a Chinese-developed resort zone -- were set to welcome visitors from November 30.

And the reopening of Siem Reap -- the gateway to the world heritage-listed Angkor Wat complex -- is brought forward from January.

Hun Sen said travellers would have to show two negative Covid tests -- one taken no less than 72 hours before travel and one on arrival in Cambodia.

"When they arrive and we see they have received two doses of vaccine, we will take swabs for rapid tests. After results show they are free of Covid-19, they are allowed to travel across Cambodia," Hun Sen said in an audio message posted on his Facebook page.

"I order the ministry of health, the ministry of tourism and relevant sectors to implement these measures from November 15, 2021 onwards," he said, adding that the move was a quick way to re-open the country.

Hor Sophea, a tour guide at Angkor Wat, welcomed the move.

"It is a positive step for the survival of our tourism," she told AFP.

Unvaccinated travellers will have to quarantine for 14 days, Hun Sen said.

Cambodia was spared the worst of the pandemic in 2020, but has recorded the bulk of its nearly 120,000 cases since April this year.

The country has won praise for its swift vaccination programme -- 88 per cent of its more than 16 million population have been fully jabbed.