Cambodian Princess Norodom Bopha Devi, a former culture minister who helped resurrect traditional Apsara dance from the ashes of the brutal Khmer Rouge rule in the 1970s, died on Monday at the age of 76, premier Hun Sen said.
Daughter of late king Norodom Sihanouk and half sister of current monarch Norodom Sihamoni, Bopha Devi died from an illness in a Bangkok hospital, according to family.
In a condolence letter shared on the prime minister's Facebook page, Hun Sen said her death marked "the greatest loss of a multi-skilled actor in the cultural sector".
He later declared November 20 a national day of mourning and for flags to fly at half-mast.
Tributes praising her contribution to the arts flooded Cambodian social media.
Prominent Cambodian filmmaker Rithy Panh tweeted "RIP Princesse Bopha Devi" with two black and white photos of her in elaborate Apsara costumes.
A classical ballet performed with slow, twisting movements and arched fingers, Apsara has been performed in Cambodia for more than 1,000 years and bas-reliefs of dancers are seen on Angkorian temple walls.
The series of gestures carry the wishes of the Khmer kings to the heavens, according to ancient custom, and was largely confined to royal circles.
It was in Cambodia's palace that Bopha Devi started dancing as a young princess, becoming the premier Apsara dancer in the 1960s and promoting the art to global acclaim.
Apsara nearly vanished in the 1970s under Cambodia's Khmer Rouge communist regime, which wiped out much of the country's heritage along with up to two million people.
After the regime fell the princess turned to training the next generation, and served as minister of culture and fine arts from 1998 to 2004.
The dance is now ubiquitous in the country, featuring in advertisements, concerts and ceremonies.
Bopha Devi's cousin Prince Sisowath Thomico told AFP the nation would remember her works to rebuild the royal ballet troupe.
"Thanks to the Princess's efforts, Cambodian Royal Ballet has been listed as world heritage," he said, referring to a United Nations list recognising "Intangible Heritage".