Kenyan officials say a civilian was killed and several policemen wounded when suspected members of the Somalia-based extremist group al-Shabab attacked a convoy of vehicles.

Interior Ministry spokesman Mwenda Njoka says the police vehicles had been escorting buses between Mombasa city and Lamu County and were destroyed in the attack.

Kenya's government is battling to stop a wave of attacks by al-Shabab fighters who say they are avenging Kenya's deployment of troops to neighboring Somalia in 2011.

Kenyan troops make up part of the African Union peacekeeping force in Somalia that bolsters the country's weak government against al-Shabab's insurgency.

Kenya's government ordered police to escort vehicles on the Lamu-Mombasa road after an al-Shabab attack last year.