Police have blamed the proscribed Mombasa Republican Council (MRC) for Saturday attacks in Lamu and Tana Delta that left 20 people dead.
Deputy Inspector General Grace Kaindi said an armed group of between 30 to 50 people attacked police officers who were manning Gamba police station.
"During the confrontation, three prisoners escaped while 10 others remained unhurt in the next cell," said Ms Kaindi at a press conference.
The attack happened at 11pm.
At exactly the same time, another group attacked Hindi area in Lamu. They burnt a church, killed 12 people and injured two.
Earlier, a spokesman for Somalia's Al-Shabaab group issued a statement claiming that their fighters had carried out the 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.