Combat between two Arab tribes in Sudan's Darfur region has killed 18 people, a resident said Sunday, adding to a growing toll as various groups battle for resources and revenge.

The latest incident occurred outside Ed Daein, the capital of East Darfur, said the resident who is a member of the local Rezeigat tribe.

"Yesterday the clash began when a Maaliya killed a Rezeigat. The Rezeigat gathered themselves for revenge but the Maaliya surrounded them and killed 18," he said, declining to be identified for security reasons.

A member of the rival Maaliya tribe said a rocket-propelled grenade destroyed a Rezeigat pickup truck used as a troop-carrying vehicle.

"I saw the Rezeigat taking away their bodies," from the vehicle, he said.

Hundreds of Rezeigat were gathering for retaliation and "a big battle might happen today or tomorrow," another resident said.

Battles between the Rezeigat and Maaliya in East Darfur last August killed 190 people, the United Nations said at the time.

Hundreds more people died in battles between other tribal groups, most of them Arab, in Darfur last year.

Inter-communal fighting has continued this year in Darfur and also in West Kordofan, which adjoins East Darfur.

Over the past two years, as Sudan's economy weakened, inter-communal clashes over resources have intensified in Darfur, a February report by UN chief Ban Ki-moon said.

Government-linked tribal militias have become involved in those conflicts, he said.

A battle last week between two sub-groups of the Misseriya tribe killed 150 people and wounded 100 more near an oil-drilling site in West Kordofan, state-linked media reported.