Darfur rebels said that 15 civilians had been killed in bombing by government planes near the Chad border, part of an offensive to rid the area of insurgents.

UN Secretary General Ban Ki-moon called on all sides to show restraint and humanitarian officials warned some 160,000 civilians dependent on aid in the area north of West Darfur's capital el-Geneina would be severely affected by the fighting.

"There were about 15 civilians killed by the aerial bombardment in Jabel Moun," Sheikh el-Din Mahin, humanitarian coordinator for the Darfur rebel Justice and Equality Movement (JEM), told Reuters by telephone from the area.

"The mountain is very big so we have not been able to gather all the injured or dead yet," he added.

Aid officials estimate some 20,000 Darfuris fled to Jabel Moun following a February 8 army attack on three nearby towns.

The Sudanese army said it had launched a "cleansing" operation in the rebel-held mountainous region to open the way for humanitarian access and to rid it of Darfur and Chadian insurgents, saying they were attacking civilians.-Reuters