Death threats outside a school and church in Sydney’s west have sparked fears in parents and parishioners.

Death threats against Christians outside a school and church in Sydney’s west have struck fear into parents and churchgoers.

Police say two men in a red hatchback hurled abuse as they drove by Maronite College of the Holy Family in Harris Park and Our Lady of Lebanon church on Wednesday.

They threatened to “kill the Christians” and slaughter their children while brandishing an Islamic State flag, a priest told AAP on Wednesday.

A distressed mother of three, who does not wish to be named, said on Thursday she did not feel safe leaving her primary school-age children at the college.

If the school did not increase security in coming months, she said she would enrol her children elsewhere.

“I know it’s not rational, but my brain shuts down and the emotions take over,” the mother said.

The raised national terrorism alert and raids in Sydney and Brisbane on Thursday fuelled her concerns, she said.

Parish priest Monsignor Shora Maree has called for calm, and has urged the community to pray for peace and refrain from creating “unnecessary panic”.

“Please do not respond to or circulate any other version of the truth on social media,” he said in a statement on Thursday.

“This is now in the hands of police, who are fully investigating.”

College spokesman Joseph Wakim told Fairfax Media the school community was shocked but stressed no students were around when the threats were made and the incident was an isolated one.

The NSW Jewish Board of Deputies is “shocked” and “appalled” by the death threats.

“The Jewish community is no stranger to such incidents and we are acutely aware of the profound impact that they have on children subjected to such abuse, on their parents and to the sense of security of members of the affected community,” chief executive officer Vic Alhadeff said in a statement.

“The incident further demonstrates that extremist ideologies pose a threat to all Australians and emphasise the need to counter violent extremism and restore social cohesion to our society.”