More than 100 people have contracted norovirus after eating raw oysters in less than a month, health authorities said on Wednesday, as they renewed calls for people to avoid having uncooked seafood.

Between January 18 and Tuesday, the Centre for Health Protection recorded 39 food poisoning cases that affected 119 people.

"Nearly 90 per cent were associated with norovirus, affecting 105 persons. Epidemiological investigations showed that all the individuals affected by the above-mentioned food poisoning cases related to norovirus had consumed raw oysters during the incubation period," the centre's controller, Edwin Tsui, said in a statement.

Officials urged residents, especially the elderly, pregnant women, children and people with weakened immune systems, to avoid eating raw oysters and undercooked shellfish.

The Centre for Food Safety earlier suspended sales of raw oysters from two suppliers amid the spike in food poisoning cases.