Harry and Meghan don Tongan dress

Meghan Markle's trend-setting dress sense usually drives frenzied shopping at her favoured designers, but her latest choice - traditional Tongan couture - might prove a little harder for fashionistas to track down.

Meghan, 37, who became the Duchess of Sussex when she married Britain's Prince Harry in May, donned garlands of red flowers and a handmade wrap skirt called ta'ovala, given as a traditional sign of respect, today as she and Harry, who also wore the traditional attire, toured the South Pacific nation of Tonga.

"I think our hearts just exploded! The #DukeandDuchessOfSussex in our national dress as they inspect traditional handicrafts," Twitter user Sulia Makasini wrote on her feed.

"What a historic moment for #Tonga."

The red and white skirts, which the two wore over their normal clothes, spelled "TONGA" in flowers at the waist and won over excited crowds in the archipelago nation, and further afield.

"They're Tongan now. Love how they embrace our culture," wrote another Twitter user, Auburn Palu, from Auckland.

The country of some 170 reef-fringed tropical islands and 108,000 people is a former British colony.

The royal couple met Tongan Prime Minister 'Akilisi Pōhiva at a government building, funded by China but named the St George Building, in the capital, Nuku'alofa.

On the way in, Harry stopped to embrace a small boy holding a sign which said "Free hugs!"

The pair, who are expecting a child of their own in the spring, were serenaded by students at Tupou College, and called in at the Royal Palace, feted everywhere by excited crowds waving flags and signs celebrating the visit.

They laughed when boys from the college sang about mosquitoes, complete with dance moves, at a ceremony to dedicate two forest reserves on the campus, where they also inspected a caged black parrot.

School children later lined the route to the airport where the couple walked over a carpet of woven mats to their plane which left for Australia in the afternoon.

Earlier on their tour, the couple visited Fiji, where enormous crowds showed up to welcome them, and Australia where the public thronged the Sydney Opera House to catch a glimpse of Queen Elizabeth's grandson and his wife.

Meghan last week wore a white cocktail dress by Australian designer Karen Gee prompting such a rush of interest that the designer's website crashed several times.