As more and more nations devise plans and strategies on how to relax the so-called lockdown restrictions and get the essential services back on track amid the COVID-19 pandemic, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus warned that the exit measures should be done extremely carefully.

"The risk of returning to lockdown remains very real if countries do not manage the transition extremely carefully and in a phased approach," he said at an online press conference from Geneva on Wednesday, Xinhua news agency reported.

He reiterated six criteria which WHO recommends countries to consider, including strong surveillance, to isolate, test and treat every case and trace every contact, sufficient preventive measures in workplaces and schools and full cooperation of the public in the post-lockdown "new norm."

According to the WHO chief, more than 3.5 million cases of COVID-19 and almost 250,000 deaths have now been reported to WHO, and since the beginning of April, an average of around 80,000 new cases have been reported every day.

"These are not just numbers -- every single case is a mother, a father, a son, a daughter, a brother, sister or friend," Tedros said.