Houses were set on fire and at least 11 villagers were killed in Kenya's Coastal region, a local elder and the Red Cross has said, in an apparent revenge attack that is part of a long-running dispute over grazing land and water.

The assailants targeted a village in the Tana Delta inhabited by Pokomo farmers late on Thursday, less than three weeks after 100 Pokomo tribesmen armed with spears and machetes attacked an Orma settlement and killed more than 50 people.

"The attack happened last night. We heard gunshots and screams, then there was smoke all over," said Jillo Dabacha, who chairs a community security group in the Tana Delta area.

"Eleven people were killed," he said.

Settled Pokomo farmers and semi-nomadic Orma pastoralists have clashed intermittently for years over access to grazing, farm land and water resources.

A Kenyan Red Cross official said local staff confirmed 11 people had been killed.

"The bodies have either gunshot wounds or burns, or both. We have been ferrying the injured to hospital since early morning," Mwanaisha Hamisi, head of the Kenyan Red Cross in Coastal province, told Reuters.

The bad blood between the two groups re-ignited late last month after the Pokomo accused the pastoralists of grazing cattle on their land.

Top Kenya government officials, among them Prime Minister Raila Odinga and Police Commissioner Mathew Iteere, have visited the area in the past few weeks, calling for calm and promising to bring the perpetrators to justice.