Police arrested seven people and ejected 15 others after a violent brawl broke out in the crowd at Friday night's NRL clash between rivals the Parramatta Eels and the Bulldogs.

Fighting first broke out inside Sydney's ANZ Stadium 10 minutes before the fulltime whistle of the game, which the Eels went on to win 26-10.

Four of those arrested for fighting were given infringement notices for offensive behaviour.

Two police officers reported being injured during the brawl, suffering a dislocated thumb and leg injuries.

There were then more arrests outside the stadium.

"Police made a further arrest for offensive language and two juveniles were detained for malicious damage," a police statement said.

"Senior police have spoken to the NRL and inquiries into the incidents continue with the issuing of banning notices to be considered."

NRL chief operating officer Graham Annesley was at the game and said he saw the fighting.

He warned violent fans they could be banned from future NRL games.

But he admitted it was hard to police the bans.

"The most important aspect of the banning notice is it puts the individuals concerned on notice so that if they do come back to our games and they do come back to our venues and they do create a disturbance, then they are committing a criminal offence," he told Macquarie Radio Network on Saturday.

"I'm not going to pretend that we have people standing on every gate in every venue trying to weed these people out.

"But it puts people on notice."

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