NSW Premier Chris Minns has promised to apply the full force of the law to tackle the "odious racism", dismissing suggestions officials have been slow to react to concerns from the Muslim community.
Police said on Friday that a mosque at Padstow, in southwest Sydney, had been the target of online hate.
The day before, a user made a comment referring to the notorious Christchurch terror attack, on a social media post from the Lakemba Mosque.
Investigators believe the incidents might be linked.
Lakemba Mosque was the second to be targeted with an online comment invoking an Australian's 2019 terrorist assault in New Zealand that left 51 worshippers dead.
A Perth teenager was recently charged over an earlier incident, in which he allegedly threatened to "Christchurch 2.0" the Australian Islamic House, also in southwest Sydney.
Mr Minns said he was appalled when the latest taunt came to light.
"I can only imagine what members of Muslim communities are going through who are in the middle of Ramadan, maybe celebrating iftar ... the last thing they need to do is deal with this kind of odious racism," he said on Friday.
But the premier rejected accusations his government had not been decisive in tackling hatred towards Muslims despite moving quickly to introduce legal changes after a spate of anti-Semitic incidents.
"If you look at the track record of both the government and NSW Police, where there's been these threats, actions have taken place, arrests have been made, charges have been laid against those individuals," he said.
Laws rushed through state parliament in February have been criticised for singling out race-based hate speech but failing to extend the same protections to religious communities.
"Sometimes the government's legislation is being characterised as only applying to one community, as if it's only there to protect one community ... it applies to every community," Mr Minns said.
Many of the anti-Semitic incidents, including the discovery of an explosives-laden caravan with references to Jewish sites, were later revealed to have been orchestrated by organised criminals to further their own ends, rather than for ideological reasons.
Gamel Kheir, secretary of the Lebanese Muslim Association, which is the custodian of the Lakemba mosque, told AAP the community was experiencing "a sense of heightened alarm".
"The Christchurch tragedy rings in our ears as it is and the community really is on edge over (the conflict in) Gaza ... their nerves are frayed," he said.
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