"People obviously spoke about this during the day and by Saturday evening a large group, maybe more than 100, had gathered.
Officers in Burnley are accused of reacting too slowly after a gang of white men allegedly launched a hammer attack on an Asian taxi driver early on Saturday.
Later on Saturday police were pelted with stones and other missiles and a pub's windows were smashed amid two hours of disturbances in the Stoneyholme area.
Delay claim
There were also a number of what police called "minor altercations" between white and Asian youths.
The deputy mayor of Burnley, Rafique Malik, said the Asian community felt angry and vulnerable because officers had taken 30 minutes to attend the taxi driver incident.
"People obviously spoke about this during the day and by Saturday evening a
large group, maybe more than 100, had gathered.
"I spoke to them personally and they were very angry about innocent people and their property being damaged.
"If the police took half an hour to arrive after the taxi driver was attacked, what faith do we have that they will protect our people?"
Mr Malik, a Labour councillor, said it would be a shame for Burnley to be tagged as "another Oldham", in a reference to disturbances in the Lancashire town at the beginning of June.
Calm restored
Overall the white community was not racist, he said, "only a few individuals".
Lancashire police, which had described the taxi driver attack as a "racially motivated incident", refused to comment on Mr Malik's accusation.
Officers had restored calm by 0100 BST on Sunday and there was no sign of trouble during the day.
The only evidence of a disturbance were the shattered windows of the Duke of York pub.
'Terrifying' attack
Landlady Marie Coulston said: "It was terrifying. About 70 of them swarmed on the pub and I had 15 windows broken.
"One brick came through the upstairs window of a room where my two children were. They could have been seriously hurt and I have moved them out of the pub for their own safety."
Burnley has around 6,000 ethnic people - mainly Pakistani and Bangladeshi - in its population of 92,000.
The far right British National Party gained 11.3% of the local vote in the general election.