JAKARTA: Authorities in Indonesia have tightened border curbs, extended quarantine and limited movement on strategic toll roads, in a preemptive move to limit the spread of the Omicron COVID-19 variant should it reach Southeast Asia's largest country.

Scientists suggest Omicron, detected so far in two dozen countries, may be more transmissible than earlier variants, threatening a global economic recovery. More than 50 countries have imposed new travel measures in recent days, according to the World Health Organization.

Indonesia, once Asia's coronavirus epicentre, has yet to announce the detection of Omicron, but is stepping up measures to minimise the potential impact, including extending the mandatory quarantine for arrival from seven days to 10.

"This policy... will be evaluated every now and then as we understand and continue digging more information about this new variant," senior minister Luhut Pandjaitan said in a statement on Wednesday.

Travel to Indonesia from 11 countries, including South Africa, Botswana, Namibia and Nigeria, will not be allowed, except for returning Indonesians, who will be subjected to 14 days of isolation.

New domestic travel measures include limiting the volume of traffic on toll roads to reduce people movement, according to the transport minister.

Official data in Indonesia shows a sharp reduction in new daily infections, with a daily average of about 400 last month compared to about 40,000 in July. More than a third of its 270 million population are vaccinated.