Police arrested the man, who they said on Friday had stabbed the imam in the stomach during prayers.
"There (was) a person in the Islamic centre who injured the imam with a knife," a police spokesman said, declining to comment on the attacker's identity.
The imam's injuries were serious but not life-threatening, the spokesman said. He said the other three were lightly wounded. The victims were taken to hospital along with the knifeman who was also hurt.
The motive was not immediately clear.