The Kenyan Parliament voted Wednesday to send military forces to the Tana Delta region to respond to ethnic fighting in which more than 100 people have been killed, Kenya's Capital FM radio reports.
Four people were killed in the region Tuesday despite a curfew imposed by Kenyan President Mwai Kibaki this week.
British Minister for Africa Mark Simmonds called on all parties to the conflict to lay down their weapons and return to the negotiating table.
"I also urge the government of Kenya to ensure that those responsible are held accountable," he said in a statement.
The Kenyan Red Cross said its staff members witnessed "hundreds of attackers" in the region, adding the humanitarian situation in the district was becoming dire.
Demonstrations turned violent last week following the slaying of Kenyan cleric Aboud Rogo Mohammed, an alleged al-Qaida sympathizer.
Fighting in the Tana district last month erupted over rival claims to pastures and water. The KRC says more than 12,000 were displaced by the fighting.
"It is clear that, in addition to an effective and proportionate security response, the underlying grievances behind this horrific violence must be properly addressed," said Simmonds.