Twelve people were killed during separate overnight attacks on Saturday in Hindi and in Tana Delta.
The heavily armed attackers invaded Gamba police station, in Garsen, Tana Delta county, killing nine people on the spot including a police officer on duty and inmates.
The attackers also released a suspected ringleader of the recent Mpeketoni attacks who was being held in the police station.
According to AFP, a spokesman for Somalia's Al-Shabaab group issued a statement claiming that their fighters had carried out another attack in the area.
"The attackers came back home safely to their base," Al-Shabaab military spokesman Abdulaziz Abu Musab said, claiming that 10 people had been killed in the attack.
Confirming the incident, the Deputy County Commissioner Mr Mike Kimoko said the attackers killed the policeman on duty, before pulling out five people held in police cells and shooting them to death.
They further pulled out other three civilians in a lorry which had just arrived at the police station and killed them before disappearing into the bush.
"Gunmen with strong power attacked the cell at around 11 o'clock and killed a policeman, five prisoners and three other civilians who had just arrived at the police station," confirmed Mr Kimoko.
He explained that the policeman who was taking charge of the cell was killed during the exchange of fire between the security officers and the attackers before they broke into the cell.
He said the attackers took advantage of the darkness in the police station, which is not connected to electricity, and it was hard to tell the total number of the attackers
No suspect has been arrested yet.
Gamba is located on the Lamu - Malindi highway towards Witu.
A separate intense gunfire was also reported at Hindi trading centre on Saturday night by unknown attackers that left three people dead and two others injured.
Hindi trading centre is located between Mpeketoni and Mokowe and is around 100 km from Gamba
The injured are being treated at Lamu hospital.
Area chief Abdalla Shahasi has confirmed the attack.
Mr Shahisi said that his office and that of the area District Officer were among the first to be attacked.
The attack comes at a time when the Deputy President William Ruto is touring the coastal region.
Mr Ruto is expected to visit Mpeketoni on Sunday to attend an interfaith prayer meeting.
Fear has engulfed residents of Gamba following the attack on the police station.
They watched in horror as the bodies of the victims of the attack were carried into a Police vehicle.
The attack comes barely a week Deputy County Commissioner Mr Kimoko expressed concern of rising tension in the area after hate leaflets were discovered in Chakamba Village, in Kipini.
The leaflets warned some communities to leave the area before July 7.
He however called on the residents to be calm as security officers continue investigating the incident.
"We have the County Commissioner and the County AP Commandant who have taken charge and I want to assure residents of safety as we continue investigating into the matter," he said.