Suspected Al-Shabaab militants on Thursday hijacked a passenger bus at Nyongoro near Witu town in Lamu County.
Lamu County Police Commander Perminus Kioi said a police officer who was escorting the bus was killed by the militants shortly after they hijacked the bus at about 10.40 am.
Three of the passengers who managed to escape from the bus alerted the police of the attack.
Mr Kioi said initial reports indicate that three people were killed immediately after the hijacking, according to information received from the three people who managed to escape.
The police commander said a team of security officers has been dispatched to the area but haven't not yet reached the scene as they waif for military back up.
The militants are said to have set the bus on fire before commanding the passengers into the forest.
The bus had about 34 to 36 passengers.