Suspected militants from the al-Shabaab group beheaded nine men in an overnight attack on a village in the Kenyan coastal district of Lamu, police said, days after Somali militants killed three policemen in an attack on a nearby village.

Police sources said Shabaab militants 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 were killed in an attack on a police post in Lamu, blamed on the Al-Qaeda aligned Shabaab.

The Shabaab 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.