An Israeli-American has been convicted of making hundreds of threats to bomb or attack Jewish schools and buildings across America, Britain and Australia.

Michael Ron David Kadar, 19, was also found guilty of extortion, money laundering and assaulting a police officer, the BBC reports.

He ran a bomb threat service, using the internet to make hoax telephone calls to the UK, America, New Zealand, Australia and Canada.

The teen was arrested in Ashkelon, Israel, in March last year, and charged in a federal court in Florida, following a joint investigation by American and Israeli authorities.

Michael Ron David Kadar, 19, (right) was arrested in Ashkelon, Israel, in March 2017

He was accused of making more than 2,000 bomb threats to Jewish organisations, police stations, sporting events, hospitals, airlines and airports

Kadar was accused of making more than 2,000 bomb threats to Jewish organisations, police stations, sporting events, hospitals, airlines and airports.

'As a result of these threats, planes were forced to land in different airports, schools were evacuated and emergency forces were alerted,' Israeli state prosecutor Yoni Hadad told a court.

'He essentially created panic, terrorised many people and disrupted their lives.'

Although it was alleged that the teenager started making threatening calls three years ago, he was only tried in relation to those made since 2016, when he turned 18.

In one February 2017 call, Kadar promised that 'in a short time, a large number of "Jew children" were going to have their heads blown off from the shrapnel,' an FBI report alleged.

The Jewish Museum in London had to be evacuated, and in February last year several British Jewish schools were targeted. Kadar also made threats involving British Airways flights between London and New York.

The calls frequently saw Kadar threatening 'bombs' and 'bloodbaths', the FBI said when he was first charged following his arrest last March.

He disguised his identity by using text-to-voice services and voice modulation software.

Judge Zvi Gurfinkel said in an Israel court that Kadar was 'well aware of the consequences of his actions' despite his parents saying he had suffered a brain tumour which had caused autism

Authorities in both the US and Israel linked Kadar to posting on the now-shuttered illicit marketplace AlphaBay advertising a 'School Email Bomb Threat Service.'

The poster offered to send customised threats to schools for $30 (£23), plus a surcharge if the buyer sought to have someone framed.

The price would increase to $45 (£34) if the buyer wanted to target more than one school or an entire district, according to the post, whose author offered refunds if a threat produced no evidence of success.

Officials claimed that he used an online calling service that disguised his voice and allowed him to hide his identity.

The threats led to evacuations, sent a chill through Jewish communities and stoked fears of rising anti-Semitism.

Investigators sought permission to search several AlphaBay accounts they believed were being operated by Kadar, including the handle 'Darknet_Legend,' according to the documents.

However, his lawyer in Jerusalem, Galit Bash, said shortly after his arrest that her client had a 'very serious medical condition' that might have affected his behaviour.

Kadar's parents have said he has a brain tumour that caused autism and other mental problems, making him unable to understand the nature of his actions.

His father told the court in Israel today that his son was ‘incapable’ of telling good from bad, and that the decision to determine Kadar fit to stand trial was ‘a lie and a conspiracy against a helpless person’.

Rejecting that claim, Judge Zvi Gurfinkel said that Kadar was 'well aware of the consequences of his actions. He understands what it means and keeps changing his version [of events] according to the convenient defence line.’

US Department of Justice charged Kadar with hate crimes and other offences

On February 28 this year, the US Department of Justice announced the indictment of Michael Ron David Kadar, 19, who holds dual United States and Israeli citizenship, in three jurisdictions for hate crimes and other offences.

It said: 'The indictment from Florida charges Kadar with hate crimes as a result of threatening calls he made to Jewish Community Centers in the state.

'In addition, the indictment from the District of Columbia charges Kadar with threatening the Israeli Embassy and the Anti-Defamation League in Washington, D.C.

'The third indictment charges him with cyberstalking and conveying false information to police dispatch regarding harm to private residents in Georgia.

'An investigation into numerous threats made to individuals and organisations throughout the United States in 2016 and early 2017 led to Kadar being charged initially in criminal complaints on April 21, 2017 in Florida and Georgia following his arrest in Israel.

'The indictment from the Middle District of Florida charges that beginning on or about January 4, 2017, and continuing until February 27, 2017, Kadar made multiple threatening calls involving bomb threats and active shooter threats to numerous Jewish Community Centers throughout Florida.

'Additionally, the indictment charges Kadar with attempting to obstruct the free exercise of religion at the Jewish Community Centers when he made the bomb threats and active shooter threats.

'Finally, the indictment charges that Kadar made bomb threats to the Orlando International Airport and a middle school in the Middle District of Florida.

'Although no actual explosives were found, many of the calls resulted in the temporary closure and evacuation or lockdown of the targeted facilities, and required law enforcement and emergency personnel to respond to and clear the area.

'The indictment from the District of Columbia charges that on or about March 7, 2017, Kadar made a threatening call to the Anti-Defamation League involving a bomb threat.

'Additionally, the indictment alleges that on or about March 9, 2017, Kadar sent a threatening email to the Israeli Embassy involving a bomb threat.

'The indictment from the Middle District of Georgia charges that on or about January 3, 2017, Kadar made a phone call to a police department conveying false information about an alleged hostage situation in progress at a private residence in Athens, Georgia, which included a threat to kill responding police officers.

'Police and emergency personnel responded to the scene, only to learn that there was no emergency.

'The hate crime charges each carry a maximum penalty of 20 years imprisonment, the bomb threats charges each carry a maximum penalty of 10 years imprisonment, and the interstate threats charge, the hoax charge, and the cyberstalking charge each carry a maximum penalty of five years imprisonment.

'If convicted, Kadar could also be subject to court ordered restitution.'

Attorney General Jeff Sessions said: 'When individuals target victims of their crimes based on who they are, what they believe, or how they worship, they target the bedrock principles on which our nation was founded.

'These alleged threats of violence instilled fear in the Jewish community and other communities across the country, and it is the Justice Department’s duty to make sure all Americans can live their lives without this type of fear.'

FBI director Christopher Wray added: 'These alleged threats were very real for those individuals who were evacuated, for the first responders who quickly mobilised to get people out of harm’s way, and for those in Jewish communities across the United States who felt targeted and unsafe.

'This indictment demonstrates the FBI’s commitment to working together with our partners to protect the safety and civil rights of all Americans, and shows that we will not stand by as someone threatens our communities based on their religion or their beliefs.'

An indictment is a formal accusation of criminal conduct, not evidence of guilt. The defendant is presumed innocent unless and until proven guilty.