Britain's Princess Charlotte, one, has spoken for the first time in public during her family's Canadian tour, uttering the word "pop" while she and her brother played with balloons.

Britain's Prince William and his wife Catherine, Duchess of Cambridge, are on a week-long trip to Canada.

It is the first time the couple have taken their children Charlotte and George, three, on an official visit to the country.

The family was in Victoria, British Columbia, on Thursday, where they attended a children's party for military families.

The event on the grounds of Government House, an official residence, included bubbles and a petting zoo with miniature ponies. But the two royal children seemed especially interested in an archway of pink and green balloons, where Charlotte was heard speaking to her brother.

It was not the first time on the tour that the children have been the centre of media attention.

Last Saturday, Prince George made headlines when he ignored Canadian Prime Minister Justin Trudeau, who was offering him a high-five and a handshake.