The RIVM National Health and Environment Institute said it "has found the corona variant Omicron in two test samples that had already been taken in the Netherlands... on November 19 and 23".

The first cases in the Netherlands had been thought to be the 14 Omicron infections on two KLM flights from South Africa that arrived in Amsterdam on Friday 26 November.

The two earlier Dutch infections also came before South Africa first reported the new strain on November 24 to the World Health Organization, which has designated the Omicron a variant of concern.

"It is not yet clear whether the people concerned (in the earlier cases) have also been to southern Africa," the RIVM said, adding that the people had been informed and municipal health services had now started contact investigations.

"In the coming period, various studies will be conducted into the distribution of the Omicron variant in the Netherlands," the institute said, adding that it would re-examine more samples from previous tests.

With 16 confirmed cases the Netherlands has one of the highest numbers in Europe of the new strain.

The airline passengers with Omicron, who were among 61 travellers on the two South Africa flights that tested positive for Covid, are currently in quarantine.

Jacaranda News/AFP