Dozens of schools around Australia have received telephoned threats over the past week in what police believe is a hoax being orchestrated overseas.

Police say the automated telephone threats, which warn of bombings or shootings at the schools, are believed to be originating from another country and none represents any legitimate danger. But the calls have been hugely disruptive. Several schools have gone into lockdown and others have ordered thousands of students to evacuate. A few children in Queensland state had to be treated for heat-related illnesses after having to wait outside their schools in sweltering temperatures.

Schools across the world have received similar threats in recent months. Police in Australia have yet to determine whether the cases are linked.