An elderly man sits with a dog in front of a closed playground, following the coronavirus disease (COVID-19) outbreak in El Masnou, north to Barcelona, Spain, April 29, 2020. REUTERS/ Albert Gea

GENEVA/LONDON: Countries must lift lockdowns gradually, while still being "on the look-out" for COVID-19 and ready to restore restrictions if the virus jumps back, the World Health Organization (WHO) said on Friday (May 1).