Five men were shot in the mosque in Maleley near the Dadaab refugee camp and two women were shot outside as they attempted to respond to the screams of the men inside, Kenyan newspaper The Standard reported.
"People were going for prayers when the attack occurred ... seven are dead," said Garissa County Commissioner Maalim Mohammed. "It is unfortunate that the attackers could not even spare women responding to cries from the mosque."
"Police are in hot pursuit for the killers," he added.
Police said they haven't established if the attack was linked to terrorism or local inter-clan feuds.
Al-Shabaab militants could be involved, Capital FM reported.