The World Health Organization on Saturday warned the coronavirus pandemic was likely to be "lengthy" as it met to evaluate the situation, six months after sounding the international alarm.

The WHO emergency committee "highlighted the anticipated lengthy duration of this COVID-19 pandemic" when it met on Friday, WHO said in a statement, warning of "the risk of response fatigue in the context of socio-economic pressures."

A surge of new infections in many parts of the world has prompted some countries to reintroduce some travel restrictions, including testing and quarantining incoming passengers.

WHO also previously acknowledged "evidence emerging" of the airborne spread of the coronavirus, after a group of scientists urged the global body to update its guidance on how the respiratory disease passes between people.

The coronavirus pandemic has claimed over 674,000 lives in 188 countries and regions since it originated in China last December.

More than 17.3 million COVID-19 cases have been reported around the world so far, with recoveries nearing 10.1 million, according to figures compiled by the Johns Hopkins University.

The U.S., Brazil, India and Russia are currently the worst-hit countries in the world.