Dutch authorities placed a couple in isolation in hospital after they absconded from a quarantine hotel, as the pair reportedly said on Monday they had been "treated like dogs".

Border police said the Portuguese man and Spanish woman were arrested on board a Spain-bound plane at Amsterdam's Schiphol Airport on Sunday.

They were among dozens of people quarantined in an airport hotel after 61 passengers on two KLM flights from South Africa on Friday tested positive for Covid-19 -- 14 of them with the new Omicron variant.

"We heard that people left the hotel, unfortunately, even if they were advised to stay there. So we had to take action and we made the arrest," Robert van Kapel, spokesman for the border police at Schiphol Airport, told AFP.

"Now they are in a place where they are isolated, in a hospital," he said.

The couple, Carolina Pimenta and Andres Sanz, told Dutch broadcaster RTL that they had both tested negative for coronavirus before leaving South Africa, but she had tested positive on arrival during a stopover in Amsterdam on the way home to Spain.

Thirteen travellers who arrived in the Netherlands from South Africa have tested positive for the new Omicron variant
Thirteen travellers who arrived in the Netherlands from South Africa have tested positive for the new Omicron variant ANP via AFP / Sem van der Wal

They insisted that after days of asking for a re-test, and two negative self-tests, a Dutch health authority official and a security guard at the Ramada quarantine hotel had said they should leave and would not get into trouble.

"The suggestion that we escaped from quarantine is too ridiculous for words. Nobody told us what the rules are, we were treated like dogs," Pimenta, who said she was a biomedical researcher, was quoted as saying by RTL.

"I know how important it is that everyone abide by the rules in this crisis," she said.

Border police then offloaded her from a flight to Spain on the tarmac, she said, adding that she was taken "with much fuss and screaming... like a criminal."

A spokeswoman for the mayor of the local Haarlemmermeer municipality confirmed the couple were "in a hospital in the Netherlands" and said they were now under investigation for a possible crime.

"These people were asked a first time to stay in the hotel, then they were asked a second time, urgently, now they are in isolation. What they did was not really wise," spokeswoman Petra Faber told AFP.

"In the Netherlands, it is not illegal to be outside when you have been tested positive (for) Covid. But when you go into a plane knowing you have it, then it is another story."

Coronavirus