The World Health Organization (WHO) urged countries to boost healthcare capacity and vaccinate their people to fight a surge in Covid-19 cases driven by the Omicron variant and said travel curbs could buy time but alone were not the answer.

Despite shutting its borders to travel from high-risk southern African countries, Australia became the latest country to report community transmission of the new variant, a day after it was found in five US states.

Omicron has gained...