A caravan has been discovered filled with explosives and a note containing addresses of Jewish people and institutions.

The vehicle was found by a resident at a property in Dural in northwest Sydney on January 19.

The note reportedly found inside the van contained addresses of Jewish people and a synagogue and included the words, "f*** the Jews".

Police are treating the incident as a credible terror threat as they continue to investigate those behind the plot.

NSW Police is working with the Australian Federal Police, NSW Crime Commission, ASIO, Victoria Police, and the Queensland Police Service to investigate the incident. NSW Police Deputy Commissioner David Hudson confirmed this on Wednesday.

"This is an ongoing investigation and is being taken seriously with all lines of inquiry being pursued," he said in a statement.

There was no ongoing threat to the community, he said.

The incident comes after a spate of anti-Semitic attacks in Sydney, with a childcare centre near a synagogue in the city's east set alight and sprayed with anti-Semitic graffiti on January 21.

Four days before, a house that formerly belonged to Executive Council of Australian Jewry co-chief executive Alex Ryvchin was targeted in an arson and graffiti attack.

Two men have been charged over a separate attack on a synagogue in Newtown after it was spray-painted with red swastikas and briefly set alight in the early hours of January 11.

Federal police have identified that foreign actors recruiting local "criminals for hire" could be behind some of the attacks targeting Jewish communities.

Cars have been set alight, a synagogue burnt down, and anti-Semitic slurs painted on buildings and cars in attacks that have escalated in frequency and severity since December.

With AAP.