Thai health authorities warned on Wednesday that residents should brace themselves for a potential jump in coronavirus cases after classifying the country's first cluster of the Omicron variant as a super-spreader incident.

The Omicron cluster identified in the northeastern province of Kalasin on Christmas eve has been linked to a couple who had travelled from Belgium and visited bars, concerts and markets.

The ensuing cluster had infected hundreds, with cases spreading to 11 other provinces, said senior health...