The Princess of Wales was accused of not being in her "own country" during a visit to Northern Ireland.
It happened when Kate and Prince William were meeting people on a walkabout in north Belfast.
A woman who shook hands with the princess said: "Nice to meet you, but it would be better if it was when you were in your own country."
The woman, who appeared to be videoing the exchange on a phone, added: "Ireland belongs to the Irish."
The prince and princess have been on a day-long trip to Northern Ireland, beginning at a suicide prevention charity in Belfast.
PIPS says it has experienced a significant increase in demand since the start of the COVID pandemic - including a 500% rise among young people.
It was founded in 2003 after 14 young people took their own lives over a short period the previous year.
They also took part in an art therapy session, painting pumpkins with vulnerable children who have been supported by PIPS.
And the couple joined a group of volunteer counsellors as they packed up the charity's Little Boxes of Hope.
As well as assisting children, the packages are designed to help parents and guardians, too.
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William, now heir to the throne, and Kate also visited a new outdoor street food and retail market in the city centre.
Trademarket, which opened its doors in July, offers artisan food, drinks and products from local, independent vendors.
The royals were pictured trying cocktails at one of the stalls.
Cheering crowds later lined the streets as they arrived in Carrickfergus, Co Antrim, to visit a youth charity.
They have been learning about the work of Carrick Connect, which offers support services to local young people experiencing social or emotional difficulties.
William and Kate met some of the young people who have benefitted and their mentors.