Eleven people have been killed in renewed ethnic clashes in a remote part of south-eastern Kenya, officials say.Armed raiders set fire to houses overnight, a local official said."We heard gunshots and screams, then there was smoke all over,” said Jillo Dabacha, according to Reuters news agency.The raid happened in the Tana River area of Coast Province, where clashes between the Orma and Pokomo communities killed at least 52 people last month."These are revenge attacks,” Kenya Red Cross official Nelly Muluka told the AFP news agency.The two groups have a long history of tension over access to land and water.The Pokomo are mostly farmers, while the Orma are semi-nomadic cattle-herders.The latest attack was on a Pokomo village, after last month’s attack on an Orma settlement, reports the Reuters news agency.