A man has been stabbed and rushed to hospital during a dramatic citizen's arrest in Melbourne CBD.

It is believed a man armed with a knife was behaving erratically in a shopping centre carpark on Lonsdale Street about 6am before he was chased down by two bystanders, Victoria Police said in a statement.

The pair followed the armed man along Elizabeth Street before they apprehended him near the intersection of Lonsdale Street.

Officers quickly responded and placed a 32-year-old Dallas man into custody.

A 41-year-old Maddingley man involved in the arrest was stabbed in the lower body and was taken hospital with a non-life-threatening injury.

A 35-year-old Sanctuary Lakes Man also involved in the arrest was unharmed.

It comes as the Public Order Response Team (PORT) have increased patrol

See Full Page