At least nine people were shot and hacked to death in Kenya's coastal Lamu County early on Saturday, officials said.
Police sources said Shabab rebels were believed to be behind the killings which took place in Jima and Pandaguo villages near the Somali border - an area that has seen a wave of recent attacks, mostly targeting the security forces.
"Nine people were killed, some were shot dead and others hacked (to death)," said a regional police officer who was not authorised to speak to the press. All the victims are civilians.
A senior officer at police headquarters in Nairobi confirmed the incident.
"It is true, we have lost nine people in today's attack," the officer said, without providing further details.
Earlier in the week, three police personnel were killed in an attack on a police post in Lamu, blamed on the al Qaeda-aligned Shabab.
"They raided Jima and Poromoko villages and killed nine men. They were slaughtered like chickens, using knives," said the witness.
Incident being assessed
Al-Shabab is fighting to overthrow the internationally-backed government in Mogadishu but also carries out regular attacks in neighbouring Kenya which has troops in Somalia as part of an African Union force.
In a televised address on Saturday morning following the death in hospital of Kenya's Interior Minister Joseph Nkaissery, President Uhuru Kenyatta spoke of "an unfortunate incident this morning, which we are assessing."
Appointing Education Minister Fred Matiangi as acting security minister Kenyatta promised there would be "no vacuum in securing our country.
Kenya goes to the polls on August 8 with Kenyatta hoping to win a second and final four-year term.
Kenya is among five countries contributing troops to an African Union force that is bolstering Somalia's fragile central government against al-Shabab's insurgency. Of the troop-contributing countries, Kenya has borne the brunt of retaliatory attacks from al-Shabab.