Police believe two men arrested at a mosque in Sydney's south on Sunday afternoon may have mental health issues.

One of the men was removed from the Arncliffe Mosque after members of the congregation became concerned by his behaviour.

Police who were outside the mosque on an unrelated matter then arrested him, along with a second man.

Both were questioned at St George Police Station, but investigators say they do not believe the men are affiliated with any specific religious group or posed any danger.