More than 40,000 people have fled clashes between two northern Kenyan tribes over access to water and pasture, the International Federation of Red Cross and Red Crescent Societies said Friday.

"We have never seen before what we are seeing this time, entire villages, entire schools destroyed, water points sabotaged," Alexander Matheou, IFRC head for East Africa, told AFP.

The UN had earlier said "tens of thousands" displaced by the fighting had fled into neighbouring Ethiopia, where the majority are living with host families.

Clashes between rival cattle herding pastoralists in the region are common, with herders often carrying guns to protect their animals, but the recent fighting has been unusually heavy.

The conflict pits two traditional rivals, the Borana and the Gabra, around the town of Moyale on the Ethiopian border.

"Shops in Moyale are closed, houses, schools are empty, there is a very eerie sense like a ghost town," Matheou said.

"Conflict between the Borana and Gabra clans in northern Kenya has displaced tens of thousands of people," the UN Office for the Coordination of Humanitarian Affairs said in a report Tuesday.

Food for 15,000 people has been sent to the area, along with plastic sheets and household items for some 3,000, it added.

Fighting over land grazing rights in the remote Moyale region killed at least 18 people last month after two days of intense violence between men armed with automatic rifles and machetes.

The Kenyan Red Cross has been attempting to mediate between the two groups.

The region was hard hit by severe drought in the Horn of Africa last year, exacerbating tensions over land in the area, and sparking tit-for-tat cattle raids.

There have been clashes going on between the Borana and the Gabra for centuries," Matheou told AFP, speaking of "coexistence with tensions built in."

Those tensions have worsened over the past decade because water points and pasture land are growing scarcer because of global warming, he said.

"That may explain why you have seen maybe a hundred people killed in the last 10 years but now... the scale is different. It appears that this is more politically motivated," he added.

Tensions have been raised by upcoming elections due by early 2013 that will usher in for the first time regional bodies with elected members and their own budgets.

Jockeying for control of the future institutions is what is behind the latest clashes, Mzalendo Kibunjia, the head of Kenya's National Cohesion and Integration Commission, said recently.

A former member of parliament from the region, Halake Guyo, was arrested late January for inciting violence.

The IFRC has distributed emergency aid but fears it will run out of money because donors are already being asked for support for three other countries in the region afflicted by conflict -- Somalia, Sudan and South Sudan.