The World Health Organization (WHO) has expressed concern over the rising rates of new COVID-19 infections and deaths, as a third wave of the virus sweeps across the world.

The agency's Director-General Tedros Adhanom said on Thursday the number of new cases per week has nearly doubled over the past two months, adding that it is approaching the highest rate of infection seen so far during the pandemic.

"This is being driven by a combination of rapidly-spreading variants, increased social mixing, inconsistent use and premature easing of public health measures, fatigued populations, and uneven and inequitable vaccine coverage," said the WHO chief.

"In some countries, despite continuing transmission, restaurants and night clubs are full and markets are crowded, with few people taking precautions."

Tedros noted that the current spike in caseloads was a predictable outcome, but was "totally avoidable."

He acknowledged that many people and countries were keen to reopen and resume normal lives, and that WHO shared in this too, but warned against hastened moves that put lives at risk.

"We urge all Member States to implement a tailored, measured, agile and evidence-based combination of measures, including surveillance, testing, contact tracing, supportive quarantine and compassionate care," he said.

He also urged people to take personal precautions to ensure their safety and the safety of those around them.

Tedros made the remarks at a Member State Information Session on COVID-19 on Thursday, as the number of infections globally surpassed the 138.4 million mark with death approaching the 3 million mark.

The world's focus has shifted to vaccinations in efforts to contain the virus. More than 700 million doses of vaccines have been administered so far, with many countries looking to ramp up their inoculations.