Fifteen people, including a regional commissioner, died when their convoy was ambushed in South Sudan's eastern Pibor region near the Ethiopian frontier, a senior official said Wednesday.

Suspected armed youths belonging to the Anyuak ethnic group from Pochalla county ambushed the convoy on Tuesday morning, said Abraham Kelang, information minister of the Greater Pibor Administrative Area.

Clashes between rival ethnic groups in South Sudan erupt frequently -- often sparked by cattle rustling and disputes over natural resources, or in retaliation for previous attacks.

Many of South Sudan's feuding communities are flush with weapons, after a five-year civil war broke out in 2013.

The convoy had only travelled 10 kilometres (six miles) when it encountered gunfire "which led to the killing of the commissioner plus 14 others", Kelang told AFP.

In addition to the commissioner of Jebel Boma county, a deputy commander of the South Sudan People's Defence Forces and a woman were among the dead.

"We found that the team that ambushed the commissioner convoy was... Anyuak," Kelang said, adding that one of the attackers was gunned down.

The motive of the attack was not immediately clear.

But Kelang accused a former commissioner who was ousted from his position in Pochalla county of mobilising the Anyuak.

One of the poorest countries on the planet despite large oil reserves, South Sudan has spent almost half of its life as a nation at war, and has also endured persistent natural disasters, hunger, economic meltdown and communal conflict.

According to the United Nations, 80 percent of the estimated 11 million population will need humanitarian aid in 2024.

A power-sharing peace agreement was signed in 2018, but many of its provisions remain unfulfilled due to ongoing disputes.

In January, fighting between rival communities in a disputed region claimed by both Sudan and South Sudan killed 54 people, including two UN peacekeepers.