Five Australian teenagers have been arrested over an alleged racial attack on a bus full of children from Jewish schools in Sydney, officials said.

Police said a group of five to 12-year-old children were travelling on a private bus to the suburb of Bondi Junction on Wednesday afternoon when eight teens jumped on.

They allegedly racially taunted the children and made physical threats, with parents claiming they yelled: "Heil Hitler", "Kill the Jews" and "Free Palestine".

None of the children was hurt but Jacqui Blackburn, whose three daughters were on the vehicle, told ABC radio they were traumatised and many were in tears.

"My little daughter said she's just really scared of everything now," she added, while questioning why the driver allowed the teenagers onto a school bus.

Arrests

Five of the eight teens were arrested overnight before being released into the custody of their parents on Thursday as investigations continued.

Yair Miller, the New South Wales Jewish Board of Deputies president, told reporters that guardians would now travel on school buses.

"This abuse is totally unacceptable, especially against the most vulnerable in our society being primary-aged children," he said.

Jason Box, the area police superintendent, told the Sydney Morning Herald that he did not believe the attack was targeted.

"In my opinion it is isolated and random and I'm hopeful that everything will be put in context for this incident," Box was quoted as saying.

Anti-Semitic attacks

Numerous anti-Semitic attacks have been reported across the world since Israel launched its offensive in Gaza.

In Britain, there have been bomb threats against synagogues. A rabbi was attacked as well and a Twitter hashtag #HitlerDidNothingWrong was circulated.

In France, pro-Palestinian rallies led to the vandalising and looting of Jewish businesses and the burning of cars.

"Gas the Jews" has been chanted at rallies in Germany.

In Casablanca, Morocco, a young man beat a rabbi until he lost consciousness.