At least 11 people have been killed in a fresh attack in Kenya's Tana River region, where months of tribal unrest has resulted in intermittent fighting.

Authorities say Thursday's attack on the Pokomo community in Kibisu was a retaliatory act that also injured several people.

It comes a day after Pokomo raiders attacked an Orma community village with guns and machetes. Nine people were killed, including at least six Orma.

Clashes between the groups have killed more than 140 people since August.

The Pokomo are farmers, while the Orma raise cattle. For years they have been at odds over land and water rights.

The recent violence has raised fears that local politicians have deepened the rift, in hopes of benefiting in Kenya's March 4 elections.

Kenya was gripped by weeks of riots and ethnic fighting after the disputed 2007 presidential poll. The violence in early 2008 killed more than 1,100 people.