Dressed in black with many wearing traditional mats, adults and schoolchildren stood or sat quietly as the caskets of the prince and his wife, Princess Kaimana Fielakepa, were taken to the funeral service in the capital.

The nation is observing a 10-day mourning period for the pair who, together with their Tongan driver, died in a car crash in California more than two weeks ago.

Tongan royal family members will observe six months of mourning, beginning with an overnight vigil at the couple's home after their bodies were returned on Thursday.

Representatives of South Pacific royalty attended the funeral, as well as dignitaries, diplomats and Tongan royal family members.

Princess Mele Siu'ilukutapu, the prince's eldest sister, told the congregation her brother had been dedicated to peaceful political reform.

The two coffins then were transported to the kingdom's ancient capital, Lapaha Village, where the pair were buried together in the Langi Na Moala tomb reserved for royalty.

Villagers along the route hung black mourning cloth from their houses and laid large tapa cloths and woven mats along the roadside as marks of respect.

The burial was overseen by traditional undertakers, known as ha'a tufunga — "half-men, half-spirits" — who tradition says guide the spirits of dead royals and nobles to Pulotu, ancient Tonga's Valhalla.

The couple were entombed atop the mound, which is regarded as tapu, or sacred, and can never be reopened.

Tu'ipelehake, a nephew of ailing 88-year-old King Taufa'ahau Topou IV, was seen by many as the one member of the royal family who believed that dialogue could resolve a growing political confrontation between the populace and the South Pacific's last ruling monarchy.

Pressure is mounting for the king to surrender his near-absolute powers to an elected parliament. The king, receiving medical treatment in New Zealand, was not at the funeral.

Tu'ipelehake headed a national committee studying democratic reforms and was in California to meet Tongans living there to hear their views.

A speeding Mustang car sideswiped the Tongans' vehicle, sending it into a roll. An 18-year-old woman has pleaded innocent to felony manslaughter charges.

The deaths stunned the Tongan community, which had just finishing celebrating King Tupou IV's birthday on July 4. The couple's driver was buried Thursday.