Jakarta: Friends and patients of two Victorian chiropractors in police custody in Jakarta have raised concerns over their arrest, saying they were respected professionals who had worked for years in Indonesia.

Thomas and Anthony Dawson, who ran six Chiropractic Indonesia clinics in Jakarta and Bali, were arrested on suspicion of treating patients when their work permits did not allow this. Police say they could face up to five years' jail.

One of Anthony Dawson's closest friends, Mark Barlow, said Dr Dawson had run a successful clinic in Geelong before moving to Indonesia more than a decade ago.

Dr Thomas Dawson ran the the Wellbeing Chiropractic clinic in Hawthorn until about three years ago.