The Police Ombudsman's office is investigating a sectarian attack on two young Catholic men in Portadown town centre at the weekend.
A police Land Rover was alleged to be nearby at the time of the gang attack.
Nationalists have questioned the alleged failure of police to spot and stop the assault.
SDLP assembly member Dolores Kelly, who has seen CCTV footage of the incident, said it was a throwback to NI's "dark days".
Police have re-issued an appeal for witnesses.
Ms Kelly said: "The trouble seen in the centre of Portadown at the weekend was unprovoked and serious.
"It is fortunate that more people were not injured after a series of prolonged and targeted attacks which spilled onto the streets and into a public carpark.
"Two young nationalists and a female police officer were injured by the loyalist mob."
'Serious disturbance'
A PSNI spokeswoman said officers were called to a report of an assault which was received at 0057 BST on Sunday and were on the scene at 0103 BST.
"One man had sustained a head injury and was taken to hospital," said the spokeswoman.
"As police attended the incident, a crowd of 20 to 30 persons gathered and a serious disturbance ensued.
"When police tried to intervene a female officer was injured and had to be taken to hospital.
"A second assault was reported to police on the scene where a male had received an injury to his eye and his arm."
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