Reports of the attack began to emerge several days ago, but the Daily Nation reports that casualties are thought to be significantly higher than an official death toll of 139 deaths.

Witnesses believe it could be at least twice as high, according to the report.

More than 3,000 Somali victims of the attack near the town of Wajjir, some with gunshot wounds, were said to have fled to safety.

The Daily Nation newspaper reported that 52 villagers - mostly teenage girls - were kidnapped and an estimated 17,500 cattle stolen and driven back towards the border.

The newspaper said the targets of the raids were reportedly from the Degodia ethnic group.

The army is combing the region in search of the attackers, and to locate people still reported missing.

The Kenyan Minister for Internal Security, Marsden Madoka, has accused Ethiopian guerrillas from the Oromo Liberation Front of being involved in the attack.

There are also reports that Ethiopian rebels from across the border might have been involved in the attack.

Reporting from Nairobi, East Africa correspondent Cathy Jenkins says that although clashes between rival nomadic groups in the region occur from time to time, the number of dead in this attack makes it the most serious for years.

Kenya's north-eastern desert province is well known for its security problems, but much of this is banditry, with weapons flowing easily across the border between Kenya and neighbouring Ethiopia and Somalia.