Police transcript from the early hours of September 18th:

Crew 1: Numerous individuals on Pavlos Melas St. and Kefallinias – around twenty people. Twenty people of Golden Dawn where we have been told that there has been an altercation with people of the known group. We are close and trying to calm tempers.

Crew 2: Perama converging too.
Crew 1: Operator, let it be known, from what we can tell, there are brass knuckles and bats.
Operator: (incomprehensible)
Crew: There is tension in the center (incomprehensible) plus one more team. Drapetsona should approach. A team should approach (incomprehensible).
Operator: Keep your distance to keep us informed. More teams are on their way.

Crew: Operator, we are noticing individuals chasing … Golden Dawn individuals chasing other individuals on Tsaldari street. They are trying to get them.
Crew 1: Nikaia here, should we converge/contribute?
Crew 2: Perama here, (incomprehensible)  
Crew: Operator, we are already on Kefallinias street. They made a left on Tsaldari towards Lambraki, we’ve lost them, approaching.
Operator: To all converging teams, 410 Perama, whoever you see making a run for it or out of breath [from running], let us know. Holding on to this until we brief… (incomprehensible)

It is evident from the dialog that police HQ was briefed that the Golden Dawn gang was targeting an anti-establishment group, however the officers on the scene were ordered not to intervene.

Following the stabbing:

Crew: Operator one individual has…he is… bleeding potentially from a stabbing. Another has told us that he was attacked. There are two men at the location. Paramedics should come.
Operator: 481, one individual injured… stabbed. Where is the individual located? Is he Greek or a foreigner?
Crew: Operator, we are on Tsaldari, Tsaldari 62. Both the victim and the person he claims is the perpetrator are Greeks.