NSW Police is considering authorising the use of "extraordinary" powers to search and identify protesters ahead of a pro-Palestinian rally in Sydney planned for Sunday.

Acting Commissioner Dave Hudson said an event by the Palestinian Action Group Sydney was deemed unauthorised this week due to a form not being submitted within the required time frame.

It followed a protest in front of Sydney Opera House earlier this week where racial epithets were chanted by some attendees.

On Monday night hundreds of people attended a pro-Palestinian rally outside the Sydney Opera House, while the landmark was lit in colours of the Israeli flag.

At the protest flares were lit by some in the crowd and thrown onto the forecourt steps, where rows of police officers were monitoring the situation.

Some protesters waved Palestinian flags and chanted slogans like "f… the Jews", "free Palestine" and "shame Israel".

No arrests were made and no-one was reported to have been injured.

Acting Commissioner Hudson on Friday said if the powers were used, police would be able to search attendees without reasonable cause and request identification, where failure to provide relevant documents would be deemed an offence.

The wider powers were introduced after the 2005 Cronulla riots and have been used "intermittently" since, the acting commissioner said.

"The powers are extensive, when the authority is granted all those powers will be available to us, however, we would not be looking to exercise the full suite of powers," Acting Commissioner Hudson said.

"Only the ones bespoke to the situation we're currently in, and we think those additional powers are required to appropriately and safely manage what is to occur on Sunday."

He warned protesters planning to attend not to go to the planned gathering, but said police are expecting between 300 and 400 people at the moment.

"We don't prohibit anyone from the right to protest but there are peaceful manners in which that could happen," Acting Commissioner Hudson said.

"People do have a right to protest, but there are responsibilities with that."