The latest fighting is reported to be in Boni forest, which straddles the border with Somalia.
Three police officers are confirmed dead and one seriously injured, according to a statement released by the Kenyan police.
Al-Shabab has claimed responsibility.
The Daily Nation newspaper reports that some 200 attackers were involved in the fighting.
It quotes a local official as saying that an unknown number of villagers are also missing.
A local communication mast has been destroyed, making it hard to get accurate information from the area.
Al-Shabab has attacked Kenya several times in recent years.
Kenyan security forces have been battling suspected al-Shabab militants for more than 10 hours after they staged a dawn attack on a police post near the coastal town of Lamu.