Many countries have not reached their peak in cases of the highly infectious Omicron variant of the coronavirus and restrictions imposed to curb its spread should be eased slowly, the World Health Organization's technical lead on COVID-19 said on Tuesday.

'We are urging caution because many countries have not gone through the peak of Omicron yet. Many countries have low levels of vaccination coverage with very vulnerable individuals within their populations,' Maria Van Kerkhove told an online briefing.

'And so now is not the time to lift everything all at once. We have always urged, always (be) very cautious, in applying interventions as well as lifting those interventions in a steady and in a slow way, piece by piece. Because this virus is is quite dynamic,' she added.

WHO's emergencies chief Mike Ryan, addressing the same briefing, urged countries to chart their own path out of the pandemic and not blindly follow others in relaxing measures.

He said he feared that political pressure might result in some countries reopening their societies prematurely, leading to unnecessary further transmissions of COVID-19 and deaths.

'I think it's a transition phase for many countries, not every country in the same situation. Those countries who are making decisions to open up more broadly, also need to be sure of capacity to reintroduce measures, with community acceptance, if needed. So as if we open the doors quickly, you better be very well able to close it very quickly as well.'

WHO Director-General Tedros Adhanom Ghebreyesus and Kerkhove also voiced concern about continued increases in the COVID-19 death toll in some countries. 'It's premature for any country to surrender or declare victory,' Tedros said.